Nonwoven fabrics comprising polylactic acid having improved strength and toughness

ABSTRACT

Nonwoven fabrics having a plurality of fibers that are bonded to each other to form a coherent web, wherein the fibers comprise a blend of a polylactic acid (PLA) and at least one secondary alkane sulfonate are provided. The nonwoven fabrics exhibit increased tensile strengths, elongation and toughness.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. ProvisionalApplication No. 62/375,648, filed Aug. 16, 2016, and the benefit of U.S.patent application Ser. No. 15/676,163, filed Aug. 14, 2017, the entirecontents of both which are hereby incorporated by reference.

FIELD

The presently-disclosed invention relates generally to nonwoven fabrics,and more particularly to nonwoven fabrics comprising polylactic acid(PLA).

BACKGROUND

Nonwoven fabrics are used in a variety of applications such as garments,disposable medical products, diapers, personal hygiene products, amongothers. New products being developed for these applications havedemanding performance requirements, including comfort, conformability tothe body, freedom of body movement, good softness and drape, adequatetensile strength and durability, and resistance to surface abrasion,pilling or fuzzing. Accordingly, the nonwoven fabrics which are used inthese types of products must be engineered to meet these performancerequirements.

Traditionally, such nonwoven fabrics are prepared from thermoplasticpolymers, such as polyester, polystyrene, polyethylene, andpolypropylene. These polymers are generally very stable and can remainin the environment for a long time. Recently, however, there has been atrend to develop articles and products that are consideredenvironmentally friendly and sustainable. As part of this trend, therehas been a desire to produce ecologically friendly products comprised ofincreased sustainable content in order to reduce the content ofpetroleum based materials.

Polylactic acid or polylactide-based polymers (PLA) provide acost-effective path to sustainable content spunbond nonwovens that canbe readily converted into consumer products. To fully capture thecost-effective benefits of PLA-based consumer products, PLA must beconvertible into nonwovens and then into the final consumer product atvery high speeds with minimal waste. However, due to the propensity ofstatic generation and accumulation on fibers with PLA polymer on thesurface, it is difficult to combine the steps of spinning, webformation, and bonding at the very high speeds needed for theeconomically attractive production of spunbond PLA with optimum fabricproperties.

To address this need, nonwovens have been developed having a sheath/corebicomponent structure in which the PLA is present in the core, and asynthetic polymer, such as polypropylene, is in the sheath. An exampleof such a nonwoven fabric is described in U.S. Pat. No. 6,506,873. Thepresence of the synthetic polymer in the sheath provides the necessaryproperties for commercial production of nonwovens comprising PLA at highspeeds. Although commercial production of nonwovens comprising PLA withsynthetic polymers in the sheath is possible, the industry (and itsconsumers) are seeking nonwovens having PLA on the surface of the fabricby either having PLA in the sheath or being 100% PLA.

Accordingly, there still exists a need for fabrics having PLA thatexhibit improved mechanical properties.

SUMMARY

One or more embodiments of the invention may address one or more of theaforementioned problems. Certain embodiments according to the inventionprovide polylactic acid (PLA) spunbond nonwoven fabrics, sustainablecomposites including said fabrics, and sustainable articles includingsaid fabrics and/or composites. In particular, embodiments of theinvention are directed to fabrics, composites, and articles comprisingPLA.

Certain embodiments according to the invention are directed to aspunbond nonwoven fabric comprising a plurality of fibers that arebonded to each other to form a coherent web, wherein the fibers comprisea blend of a polylactic acid (PLA) and at least one secondary alkanesulfonate. In some embodiments, the blend is present at a surface of theplurality of fibers.

In one embodiment, the at least one secondary alkane sulfonate comprisesan alkane chain having from C₁₀-C₁₈, and wherein at least one of thesecondary carbons of the alkane chain includes a sulfonate moiety. Forexample, the at least one secondary alkane sulfonate has one of thefollowing structures:

wherein m+n is a number between 7 and 16, and X is independently a C₁-C₄alkyl or absent. In some embodiments, the at least one secondary alkanesulfonate has the following structure:

wherein m+n is a number between 8 and 15, and in particular, wherein m+nis a number between 11 and 14. In some embodiments, the at least onesecondary alkane sulfonate comprises a salt of sodium or potassium.

In certain embodiments, the at least one secondary alkane sulfonate ispresent in an amount ranging from about 0.0125 to 2.5 weight percent,based on the total weight of the fiber. For example, the fiber may havea sheath/core bicomponent arrangement in which the blend is present inthe sheath, and wherein the secondary alkane sulfonate is present in thesheath in an amount ranging from about 0.1 to 0.75 weight percent, basedon the total weight of the sheath. In another embodiment, the fiber mayhave a sheath/core bicomponent arrangement in which the blend is presentin the sheath, and wherein the secondary alkane sulfonate is present inthe sheath in an amount ranging from about 0.2 to 0.6 weight percent,based on the total weight of the sheath. In yet another embodiment, thefiber has a sheath/core bicomponent arrangement in which the blend ispresent in the sheath, and wherein the secondary alkane sulfonate ispresent in the sheath in an amount ranging from about 0.3 to 0.4 weightpercent, based on the total weight of the sheath.

In one embodiment, the plurality of fibers comprise bicomponent fibers.In some embodiments, the plurality of fibers comprise bicomponent fibersand the at least one secondary alkane sulfonate is present in only oneof the component of the fibers. In one embodiment, the bicomponentfibers have a sheath/core configuration and the sheath comprises a blendof the PLA and the at least one secondary alkane sulfonate. In someembodiments, the core comprises PLA and does not include the at leastone secondary alkane sulfonate. In still other embodiments, thebicomponent fibers comprise a side-by-side arrangement.

In one embodiment, the core comprises at least one of a polyolefin, apolyester, a PLA, or any combination thereof. In a preferred embodiment,each of the sheath and the core comprises PLA. In certain embodiments,the sheath comprises a first PLA grade, the core comprises a second PLAgrade, and the first PLA grade and the second PLA grade are different.

Surprisingly, the inventors have discovered that the addition of thesecondary alkane sulfonate to the PLA resin improves the mechanicalproperties of the fabric. In particular, the fabric may exhibit anincrease in tensile strength, elongation and toughness in at least oneof the machine direction or cross direction in comparison to anidentical fabric that does not include the at least one secondary alkanesulfonate. For example, the fabric may exhibit an increase in tensilestrength in at least one of the machine direction or cross direction ofat least 50% in comparison to an identical fabric that does not includethe at least one secondary alkane sulfonate.

In yet another aspect, embodiments of the invention are directed to aspunbond nonwoven fabric comprising a plurality of fibers that arebonded to each other to form a coherent web, wherein the fibers comprisefrom 95 to 100% polylactic acid (PLA), and wherein the fibers exhibit aroot mean square of a Toughness Index per basis weight having a valuethat is at least 55 N/m². In one embodiment, the fabric has a root meansquare of the Toughness Index per basis weight is a value that isgreater than 65 N-%/g/m², such as a value that is greater than 85N-%/g/m². In a preferred embodiment, the fabric has a root mean squareof the Toughness Index per basis weight is a value from about from about65 to 150 N-%/g/m². Preferably, the fabric comprises fibers having lessthan 5 weight % of additives, and more preferably less than 4 weight %,based on the total weight of the fabric.

Additional aspects of the invention are directed to articles comprisingthe nonwoven fabric and to a process and system for preparing thefabric.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

Having thus described the invention in general terms, reference will nowbe made to the accompanying drawings, which are not necessarily drawn toscale, and wherein:

FIGS. 1A and 1B are SEM images of individual bond points on a surface ofa nonwoven fabric that does not include a secondary alkane sulfonate;

FIGS. 2A and 2B are SEM images of individual bond points on a surface ofa nonwoven fabric that includes a secondary alkane sulfonate;

FIG. 3 is a schematic diagram of the PLA spunbond nonwoven fabricpreparation system in accordance with certain embodiments of theinvention;

FIGS. 4A-4C are schematic diagrams illustrating positioning of the firstionization source in accordance with certain embodiments of theinvention;

FIGS. 5A-5D are cross-sectional views of composites in accordance withcertain embodiments of the invention;

FIG. 6A is an illustration of an absorbent article in accordance with atleast one embodiment of the invention;

FIG. 6B is a cross-sectional view of the absorbent article of FIG. 6Ataken along line 72-72 of FIG. 6A; and

FIG. 7 is an illustration of an absorbent article in accordance with atleast one embodiment of the invention in which the absorbent article isin the form of a feminine sanitary pad.

DETAILED DESCRIPTION

The invention now will be described more fully hereinafter withreference to the accompanying drawings, in which some, but not allembodiments of the inventions are shown. Indeed, this inventions may beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will satisfy applicable legalrequirements. Like numbers refer to like elements throughout. As used inthe specification, and in the appended claims, the singular forms “a”,“an”, “the”, include plural referents unless the context clearlydictates otherwise.

The invention includes, according to certain embodiments, polylacticacid (PLA) spunbond nonwoven fabrics, sustainable composites includingsaid fabrics, and absorbent articles including said fabrics and/orcomposites. In particular, embodiments of the invention are directed tofabrics, composites, and articles in which PLA is present on the fabricsurface.

PLA spunbond nonwoven fabrics and sustainable composites including saidfabrics may be used in a wide variety of applications, includingdiapers, feminine care products, wiper products, incontinence products,agricultural products (e.g., root wraps, seed bags, crop covers and/orthe like), industrial products (e.g., work wear coveralls, airlinepillows, automobile trunk liners, sound proofing articles and/or thelike), and household products (e.g., furniture scratch pads, mattresscoil covers and/or the like).

I. Definitions

For the purposes of the present application, the following terms shallhave the following meanings:

The term “fiber” can refer to a fiber of finite length or a filament ofinfinite length.

As used herein, the term “monocomponent” refers to fibers formed fromone polymer or formed from a single blend of polymers. Of course, thisdoes not exclude fibers to which additives have been added for color,anti-static properties, lubrication, hydrophilicity, liquid repellency,etc.

As used herein, the term “multicomponent” refers to fibers formed fromat least two polymers (e.g., bicomponent fibers) that are extruded fromseparate extruders. The at least two polymers can each independently bethe same or different from each other, or be a blend of polymers. Thepolymers are arranged in substantially constantly positioned distinctzones across the cross-section of the fibers. The components may bearranged in any desired configuration, such as sheath-core,side-by-side, pie, island-in-the-sea, and so forth. Various methods forforming multicomponent fibers are described in U.S. Pat. No. 4,789,592to Taniguchi et al. and U.S. Pat. No. 5,336,552 to Strack et al., U.S.Pat. No. 5,108,820 to Kaneko, et al., U.S. Pat. No. 4,795,668 to Kruege,et al., U.S. Pat. No. 5,382,400 to Pike, et al., U.S. Pat. No. 5,336,552to Strack, et al., and 6,200,669 to Marmon, et al., which areincorporated herein in their entirety by reference. Multicomponentfibers having various irregular shapes may also be formed, such asdescribed in U.S. Pat. No. 5,277,976 to Hogle, et al., U.S. Pat. No.5,162,074 to Hills, U.S. Pat. No. 5,466,410 to Hills, U.S. Pat. No.5,069,970 to Largman, et al., and 5,057,368 to Largman, et al., whichare incorporated herein in their entirety by reference.

As used herein, the terms “nonwoven,” “nonwoven web” and “nonwovenfabric” refer to a structure or a web of material which has been formedwithout use of weaving or knitting processes to produce a structure ofindividual fibers or threads which are intermeshed, but not in anidentifiable, repeating manner. Nonwoven webs have been, in the past,formed by a variety of conventional processes such as, for example,meltblown processes, spunbond processes, and staple fiber cardingprocesses.

As used herein, the term “meltblown” refers to a process in which fibersare formed by extruding a molten thermoplastic material through aplurality of fine, usually circular, die capillaries into a highvelocity gas (e.g. air) stream which attenuates the molten thermoplasticmaterial and forms fibers, which can be to microfiber diameter.Thereafter, the meltblown fibers are carried by the gas stream and aredeposited on a collecting surface to form a web of random meltblownfibers. Such a process is disclosed, for example, in U.S. Pat. No.3,849,241 to Buntin et al.

As used herein, the term “machine direction” or “MD” refers to thedirection of travel of the nonwoven web during manufacturing.

As used herein, the term “cross direction” or “CD” refers to a directionthat is perpendicular to the machine direction and extends laterallyacross the width of the nonwoven web.

As used herein, the term “spunbond” refers to a process involvingextruding a molten thermoplastic material as filaments from a pluralityof fine, usually circular, capillaries of a spinneret, with thefilaments then being attenuated and drawn mechanically or pneumatically.The filaments are deposited on a collecting surface to form a web ofrandomly arranged substantially continuous filaments which canthereafter be bonded together to form a coherent nonwoven fabric. Theproduction of spunbond non-woven webs is illustrated in patents such as,for example, U.S. Pat. Nos. 3,338,992; 3,692,613, 3,802,817; 4,405,297and 5,665,300. In general, these spunbond processes include extrudingthe filaments from a spinneret, quenching the filaments with a flow ofair to hasten the solidification of the molten filaments, attenuatingthe filaments by applying a draw tension, either by pneumaticallyentraining the filaments in an air stream or mechanically by wrappingthem around mechanical draw rolls, depositing the drawn filaments onto aforaminous collection surface to form a web, and bonding the web ofloose filaments into a nonwoven fabric. The bonding can be any thermalor chemical bonding treatment, with thermal point bonding being typical.

As used herein, the term “thermal point bonding” involves passing amaterial such as one or more webs of fibers to be bonded between aheated calender roll and an anvil roll. The calender roll is typicallypatterned so that the fabric is bonded in discrete point bond sitesrather than being bonded across its entire surface.

As used herein, the term “polymer” generally includes, but is notlimited to, homopolymers, copolymers, such as, for example, block,graft, random and alternating copolymers, terpolymers, etc. and blendsand modifications thereof. Furthermore, unless otherwise specificallylimited, the term “polymer” shall include all possible geometricalconfigurations of the material, including isotactic, syndiotactic andrandom symmetries.

The term “composite”, as used herein, may be a structure comprising twoor more layers, such as a film layer and a fiber layer or a plurality offiber layers molded together. The two layers of a composite structuremay be joined together such that a substantial portion of their commonX-Y plane interface, according to certain embodiments of the invention.

Embodiments of the invention are directed to nonwoven fabrics comprisingpolylactic acid that exhibit improvements in strengths and toughness. Inone embodiment, the present invention provides a spunbond nonwovenfabric comprising a plurality of fibers that are bonded to each other toform a coherent web, and wherein the plurality fibers comprise a blendof a PLA resin and at least one secondary alkane sulfonate. As explainedin greater detail below, the inclusion of a secondary alkane sulfonatein the PLA resin improves the strength and toughness of the fabric incomparison to an identical fabric that does not include the secondaryalkane sulfonate.

The at least one secondary alkane sulfonate typically comprises analkane chain having from C₁₀-C₁₈, and wherein at least one of thesecondary carbons of the alkane chain includes a sulfonate moiety. Inparticular, the at least one secondary alkane sulfonate may comprise asulfonic acid, C13-C17-secondary alkane, sodium salt.

The alkane chain is generally linear although some chains may includesome minor branching (e.g., C₁-C₄ side chain branching). Typically, thealkane chain will have from 10 to 18 carbon atoms, with an alkane chainlength of 14 to 17 carbon atoms being somewhat more preferred. Thesecondary alkane sulfonate may include both mono- and disulfonic acids.However, the amount of monosulfonic acids in the secondary alkanesulfonate may generally be greater than 90%.

In one embodiment, the at least one secondary alkane sulfonate has oneof the following structures:

wherein m+n is a number between 7 and 16, and X is independently a C₁-C₄alkyl or absent. In a preferred embodiment, the secondary alkanesulfonate has the following structure:

wherein m+n is a number between 8 and 15, and more preferably m+n is anumber between 11 and 14. The secondary alkane sulfonate typicallycomprises a salt of sodium or potassium, but other cations could beused, such as a salt of calcium or magnesium. Alternatively, aquaternary ammonium comprised of modified fatty alkyl substrates such asthose based on coco or stearyl substrates could be used. Such quaternaryamines are available from Air Products and Chemicals, Inc. of Allentown,Pa. 18195-1501, USA.

In one embodiment, the secondary alkane sulfonate may be provided in amasterbatch carrier resin. For example, in one embodiment, the secondaryalkane sulfonate is provided in a PLA polymer carrier resin that isblended with the PLA prior to spinning of the fibers. Typically, theamount of secondary alkane sulfonate in the PLA masterbatch is fromabout 5 to 25 weight percent based on the total weight of themasterbatch, with an amount from 10 to 20 weight percent being somewhatmore typical. The masterbatch may also include additional additives,such as one or more compatibilizers. A commercial example of a secondaryalkane sulfonate that may be used in embodiments of the claimedinvention includes SUKANO® under the product name 5546-Q1, which is aC14-C17 secondary alkane sulfonate sodium salt in a PLA masterbatch. Oneskilled in the art would recognize that design of a masterbatch for asecondary alkane sulfonate is a compromise between maximizing the use ofPLA resins with very similar melt flow as observed for the base resin ofthe fiber, such as, for example, NatureWorks 6202D or 6252 D (Melt Indexg/10 minutes (210° C.) 15-30 or 15, respectively, and the ease ofsuspending the secondary alkane sulfonate in a PLA polymer. Thus, asuitable masterbatch may be comprised of a PLA grade such as NatureWorks 6362D with a higher melt Index (Melt Index g/10 minutes (210° C.)of 70-85.

A wide variety of different PLA resins may be used to prepare nonwovenfabrics in accordance with embodiments of the invention. Generally,polylactic acid based polymers are prepared from dextrose, a source ofsugar, derived from field corn. In North America corn is used since itis the most economical source of plant starch for ultimate conversion tosugar. However, it should be recognized that dextrose can be derivedfrom sources other than corn. Sugar is converted to lactic acid or alactic acid derivative via fermentation through the use ofmicroorganisms. Lactic acid may then be polymerized to form PLA. Inaddition to corn, other agricultural based sugar sources may be usedincluding rice, sugar beets, sugar cane, wheat, cellulosic materials,such as xylose recovered from wood pulping, and the like.

The PLA resin should have proper molecular properties to be spun inspunbond processes. Examples of suitable include PLA resins are suppliedfrom NatureWorks LLC, of Minnetonka, Minn. 55345 such as, grade 6752D,6100D, and 6202D, which are believed to be produced as generallyfollowing the teaching of U.S. Pat. Nos. 5,525,706 and 6,807,973 both toGruber et al. Other examples of suitable PLA resins may include L130,L175, and LX175, all from Corbion of Arkelsedijk 46, 4206 A C Gorinchem,the Netherlands.

In some embodiments, the nonwoven fabrics may be biodegradable.“Biodegradable” refers to a material or product which degrades ordecomposes under environmental conditions that include the action ofmicrorganisms. Thus, a material is considered as biodegradable if aspecified reduction of tensile strength and/or of peak elongation of thematerial or other critical physical or mechanical property is observedafter exposure to a defined biological environment for a defined time.Depending on the defined biological conditions, a fabric comprised ofPLA might or might not be considered biodegradable.

A special class of biodegradable products made with a bio-based materialmight be considered as compostable if it can be degraded in a composingenvironment. The European standard EN 13432, “Proof of Compostability ofPlastic Products” may be used to determine if a fabric or film comprisedof sustainable content could be classified as compostable.

In some embodiments, the PLA nonwoven fabrics may comprise sustainablepolymer components of biodegradable products that are derived from analiphatic component possessing one carboxylic acid group (or a polyesterforming derivative thereof, such as an ester group) and one hydroxylgroup (or a polyester forming derivative thereof, such as an ethergroup) or may be derived from a combination of an aliphatic componentpossessing two carboxylic acid groups (or a polyester forming derivativethereof, such as an ester group) with an aliphatic component possessingtwo hydroxyl groups (or a polyester forming derivative thereof, such asan ether group).

The term “aliphatic polyester” covers—besides polyesters which are madefrom aliphatic and/or cycloaliphatic components exclusively alsopolyesters which contain besides aliphatic and/or cylcoaliphatic unitsaromatic units, as long as the polyester has substantial sustainablecontent.

In addition to PLA based resins, nonwoven fabrics in accordance withembodiments of the invention may include other polymers derived from analiphatic component possessing one carboxylic acid group and onehydroxyl group, which are alternatively called polyhydroxyalkanoates(PHA). Examples thereof are polyhydroxybutyrate (PHB),poly-(hydroxybutyrate-co-hydroxyvaleterate) (PHBV),poly-(hydroxybutyrate-co-polyhydroxyhexanoate) (PHBH), polyglycolic acid(PGA), poly-(epsilon-caprolactione) (PCL) and preferably polylactic acid(PLA).

Examples of additional polymers that may be used in embodiments of theinvention include polymers derived from a combination of an aliphaticcomponent possessing two carboxylic acid groups with an aliphaticcomponent possessing two hydroxyl groups, and are polyesters derivedfrom aliphatic diols and from aliphatic dicarboxylic acids, such aspolybutylene succinate (PBSU), polyethylene succinate (PESU),polybutylene adipate (PBA), polyethylene adipate (PEA),polytetramethy-lene adipate/terephthalate (PTMAT).

Nonwoven fabrics in accordance with the invention may comprisemonocomponent, bicomponent, or multicomponent fibers. Examples ofbicomponent fibers include side-by-side, islands in the sea, andsheath/core arrangements. Preferably, the fibers have a sheath/corestructure in which the sheath comprises a first polymer component, andthe core comprises a second polymer component. In this arrangement, thepolymers of the first and second polymer components may be the same ordifferent from each other.

In a preferred embodiment, the fibers of the nonwoven fabric have abicomponent arrangement in which the PLA blend comprising the secondaryalkane sulfonate comprises a first polymer component defining a sheath,and a second polymer component comprises the core. Advantageously, theinventors have discovered that by blending the secondary alkanesulfonate into the polymer component defining the sheath, nonwovenfabrics having improved strength and toughness are provided. Inaddition, such improvements in physical properties may be obtainable inthe absence of blending the secondary alkane sulfonate into the polymercomponent defining the core, which may help reduce the overall costs ofpreparing the nonwoven fabric.

In preferred embodiments, the sheath and the core both comprise a PLAresin. In these embodiments, a PLA spunbond nonwoven fabric may beprovided that is substantially free of synthetic polymer components,such as petroleum-based materials and polymers. For example, the fibersof the PLA spunbond nonwoven fabric may have a bicomponent arrangementin which the both components are PLA based to thus produce a fiber thatis 100% PLA.

As used herein, “100% PLA” may also include up to 5% additives includingadditives and/or masterbatches of additives to provide, by way ofexample only, color, softness, slip, antistatic protection, lubricity,hydrophilicity, liquid repellency, antioxidant protection and the like.In this regard, the nonwoven fabric may comprise 95-100% PLA, such asfrom 96-100% PLA, 97-100% PLA, 98-100% PLA, 99-100% PLA, etc. When suchadditives are added as a masterbatch, for instance, the masterbatchcarrier may primarily comprise PLA in order to facilitate processing andto maximize sustainable content within the fibers.

For example, the PLA spunbond nonwoven fabric layer may comprise one ormore additional additives. In such embodiments, for instance, theadditive may comprise at least one of a colorant, a softening agent, aslip agent, an antistatic agent, a lubricant, a hydrophilic agent, aliquid repellent, an antioxidant, and the like, or any combinationthereof.

In one embodiment, the PLA polymer of the sheath may be the same PLApolymer as that of the core. In other embodiments, the PLA polymer ofthe sheath may be a different PLA polymer than that of the core. Forexample, the bicomponent fibers may comprise PLA/PLA reverse bicomponentfibers such that the sheath comprises a first PLA grade, the corecomprises a second PLA grade, and the first PLA grade and the second PLAgrade are different (e.g., the first PLA grade has a higher meltingpoint than the second PLA grade). By way of example only, the first PLAgrade may comprise up to about 5% crystallinity, and the second PLAgrade may comprise from about 40% to about 50% crystallinity.

In other embodiments, for instance, the first PLA grade may comprise amelting point from about 125° C. to about 135° C., and the second PLAgrade may comprise a melting point from about 155° C. to about 170° C.In further embodiments, for example, the first PLA grade may comprise aweight percent of D isomer from about 4 wt. % to about 10 wt. %, and thesecond PLA grade may comprise a weight percent of D isomer of about 2wt. %.

For example, in one embodiment, the core may comprise a PLA having alower % D isomer of polylactic acid than that of the % D isomer PLApolymer used in the sheath. The PLA polymer with lower % D isomer willshow higher degree of stress induced crystallization during spinningwhile the PLA polymer with higher D % isomer will retain a moreamorphous state during spinning. The more amorphous sheath will promotebonding while the core showing a higher degree of crystallization willprovide strength to the fiber and thus to the final bonded web. In oneparticular embodiment, the Nature Works PLA Grade PLA 6752 with 4% DIsomer can be used as the sheath while NatureWorks Grade 6202 with 2% DIsomer can be used as the core.

Generally, the weight percentage of the sheath to that of the core inthe fibers may vary widely depending upon the desired properties of thenonwoven fabric. For example the weight ratio of the sheath to the coremay vary between about 10:90 to 90:10, and in particular from about20:80 to 80:20. In a preferred embodiment, the weight ratio of thesheath to the core is about 25:75 to 35:65, with a weight ratio of about30:70 being preferred.

In other embodiments, a nonwoven fabric comprising bicomponent fibers isprovided in which one of the polymer components comprises a blend of aPLA polymer and the secondary alkane sulfonate, and the other polymercomponent comprises a synthetic polymer, such as a petroleum derivedpolymer. Examples of synthetic polymers that may be used in embodimentsof the invention may include polyolefins, such as polypropylene andpolyethylene, polyesters, such as polyethylene terephthalate (PET),polytrimethylene terephthalate (PTT), and polybutylene terephthalate(PBT), nylons, polystyrenes, copolymers, and blends thereof, and othersynthetic polymers that may be used in the preparation of fibers.

The amount of the secondary alkane sulfonate in the fibers willgenerally depend on where the secondary alkane sulfonate is present inthe structure of the fibers, and the final desired properties of thenonwoven fabric. In general, the amount of the secondary alkanesulfonate may range from about 0.0125 weight percent to about 2.5 weightpercent, based on the total weight of the polymeric component of thefiber in which the secondary alkane sulfonate is present. For example,in monocomponent fibers the weight percent of the secondary alkanesulfonate in the fibers will be based on the total weight of the fiber.In such a case, the amount secondary alkane sulfonate may range fromabout 0.0125 weight percent to about 2.5 weight percent, based on thetotal weight of the fiber. However, in the case of a bicomponent fiber,the weight percent of the secondary alkane sulfonate will be based onthe total weight of the component in which the secondary alkanesulfonate is present. For example, in the case of a bicomponent fiberhaving a sheath to core weight ratio of 30:70, and in which thesecondary alkane sulfonate is only present in the sheath, the weightpercent of the secondary alkane sulfonate in the fiber may range fromabout 0.0125 weight percent to about 2.5 weight percent, based on thetotal weight of the sheath, which results in a weight percent of thesecondary alkane sulfonate that is from 0.00375 to 0.750, based on thetotal weight of the fiber.

In one embodiment, the amount of the secondary alkane sulfonate may beat least about any one of the following: at least 0.0125, at least0.0250, at least 0.0375, at least 0.050, at least 0.0625, at least0.075, at least 0.100, at least 0.125, at least 0.150, at least 0.1875,at least 0.2, at least 0.2475, at least 0.25, at least 0.3 at least0.375, at least 0.40, at least 0.495, at least 0.50, at least 0.60, atleast 0.80, at least 0.9904, at least 1.0, at least 1.25, at least1.2375, at least 1.5, at least 1.875, at least 2.0, and at least 2.50,based on the total weight of the polymeric component of the fiber inwhich the secondary alkane sulfonate is present. In other embodiments,the amount of the secondary alkane sulfonate may be less than about anyone of the following: 0.0250, 0.0375, 0.050, 0.0625, 0.075, 0.100,0.125, 0.150, 0.1875, 0.2, 0.2475, 0.25, 0.3, 0.375, 0.40, 0.495, 0.50,0.60, 0.80, 0.9904, 1.0, 1.25, 1.2375, 1.5, 1.875, 2.0, and 2.50 weightpercent. It should also be recognized that the amount of the secondaryalkane sulfonate present in a polymer component of the fiber alsoencompasses ranges between the aforementioned amounts.

In a preferred embodiment, the fibers have a bicomponent structure inwhich the core and sheath both comprise a PLA polymer, and the sheathincludes the secondary alkane sulfonate that is present in an amountthat is from about 0.1 to 1 weight percent, based on the total weight ofthe sheath component, and in particular, from about 0.1 to 0.75, andmore particularly from about 0.2 to 0.6 weight percent, and even moreparticularly, from about 0.3 to 0.4 weight percent, based on the totalweight of the sheath component. Although, the secondary alkane sulfonatehas generally discussed as being present in a monocomponent fiber or thesheath of a bicomponent fiber, it should be recognized that otherarrangements are within the embodiments of the present invention. Forexample, the secondary alkane sulfonate may be present in only the coreand not the sheath of a bicomponent fiber, or the secondary alkanesulfonate may be present in both the sheath and the core.

As the amount of the secondary alkane sulfonate in the fibers may varydepending on the amount of the secondary alkane sulfonate in themasterbatch polymer, the structure of the fiber (e.g., monocomponent orbicomponent), and in the case of the bicomponent, the ratio of a firstpolymer component to a second component in the fiber, the followingtables provide exemplary ranges of the secondary alkane sulfonate invarious fiber structures and at various loadings of the secondary alkanesulfonate in the masterbatch polymer, and at various loadings of themasterbatch in the PLA polymer.

TABLE 1A Amounts of the Secondary Alkane Sulfonate (SAS) in the Sheathof a bicomponent fiber having a sheath to core weight ratio of 50:50 atvarious SAS and Master Batch (MB) loadings Amount Amount Amount Amountof SAS of SAS of SAS of SAS in Sheath at in Sheath at in Sheath at inSheath at an addition an addition an addition an addition Amount of 5%MB of 10% MB of 20% MB of 25% MB of SAS to Sheath to Sheath to Sheath toSheath in MB polymer polymer polymer polymer (%) (%) (%) (%) (%) 0.25%0.0125 0.025 0.050 0.0625 0.50% 0.025 0.050 0.100 0.125 0.75% 0.03750.075 0.150 0.1875 1.0% 0.050 0.100 0.200 0.250 2.0% 0.100 0.200 0.4000.500 3.0% 0.150 0.300 0.600 0.750 4.0% 0.200 0.400 0.800 1.000 4.95%0.2475 0.495 0.9904 1.2375 5.0% 0.250 0.500 1.00 1.2500 7.5% 0.375 0.7501.500 1.8750 10.0% 0.500 1.000 2.000 2.5000

TABLE 1B Amounts of the Secondary Alkane Sulfonate (SAS) in the Fabriccomprised of bicomponent fibers having a sheath to core weight ratio of50:50 at various SAS and Master Batch (MB) loadings Amount Amount AmountAmount of SAS of SAS of SAS of SAS in Fabric at in Fabric at in Fabricat in Fabric at an addition an addition an addition an addition Amountof 5% MB of 10% MB of 20% MB of 25% MB of SAS to Sheath to Sheath toSheath to Sheath in MB polymer polymer polymer polymer (%) (%) (%) (%)(%) 0.25% 0.00625 0.0125 0.025 0.03125 0.50% 0.01250 0.025 0.050 0.062500.75% 0.01875 0.0375 0.075 0.09375 1.0% 0.02500 0.050 0.100 0.12500 2.0%0.05000 0.100 0.200 0.25000 3.0% 0.07500 0.150 0.300 0.37600 4.0%0.10000 0.200 0.400 0.50000 4.95% 0.12375 0.2475 0.495 0.61875 5.0%0.12500 0.250 0.500 0.62500 7.5% 0.18750 0.375 0.750 0.93750 10.0%0.25000 0.500 1.000 1.25000

TABLE 2A Amounts of the Secondary Alkane Sulfonate (SAS) in Sheath of abicomponent fiber having a sheath to core weight ratio of 30:70 atvarious SAS and Master Batch (MB) loadings Amount Amount Amount Amountof SAS of SAS of SAS of SAS in Sheath at in Sheath at in Sheath at inSheath at an addition an addition an addition an addition Amount of 5%MB of 10% MB of 20% MB of 25% MB of SAS to Sheath to Sheath to Sheath toSheath in MB polymer polymer polymer polymer (%) (%) (%) (%) (%) 0.25%0.0125 0.025 0.050 0.0625 0.50% 0.025 0.050 0.100 0.125 0.75% 0.03750.075 0.150 0.1875 1.0% 0.050 0.100 0.200 0.250 2.0% 0.100 0.200 0.4000.500 3.0% 0.150 0.300 0.600 0.750 4.0% 0.200 0.400 0.800 1.000 4.95%0.2475 0.495 0.9904 1.2375 5.0% 0.250 0.500 1.00 1.2500 7.5% 0.375 0.7501.500 1.8750 10.0% 0.500 1.000 2.000 2.5000

TABLE 2B Amounts of the Secondary Alkane Sulfonate (SAS) in a Fabriccomprising bicomponent fibers having a sheath to core weight ratio of30:70 at various SAS and Master Batch (MB) loadings Amount Amount AmountAmount of SAS of SAS of SAS of SAS in Fabric at in Fabric at in Fabricat in Fabric at an addition an addition an addition an addition Amountof 5% MB of 10% MB of 20% MB of 25% MB of SAS to Sheath to Sheath toSheath to Sheath in MB polymer polymer polymer polymer (%) (%) (%) (%)(%) 0.25% 0.00375 0.0075 0.015 0.01875 0.50% 0.00750 0.0150 0.03000.0375 0.75% 0.01125 0.0225 0.04500 0.05625 1.0% 0.0150 0.0300 0.06000.0750 2.0% 0.030 0.060 0.1200 0.1500 3.0% 0.0450 0.0900 0.1800 0.22504.0% 0.0600 0.1200 0.2400 0.3000 4.95% 0.07425 0.1485 0.2970 0.371255.0% 0.0750 0.1500 0.3000 0.375 7.5% 0.1125 0.2250 0.4500 0.5625 10.0%0.1500 0.3000 0.6000 0.7500

TABLE 3 Amounts of the Secondary Alkane Sulfonate (SAS) in a Fabriccomprising PLA monocomponent fibers at various SAS and Master Batch (MB)loadings Amount Amount Amount Amount of SAS in of SAS in of SAS in ofSAS in Amount Fabric at Fabric at Fabric at Fabric at of SAS an additionan addition an addition an addition in MB of 5% MB of 10% MB of 20% MBof 25% (%) (%) (%) (%) (%) 0.25% 0.0125 0.025 0.050 0.0625 0.50% 0.0250.050 0.100 0.125 0.75% 0.0375 0.075 0.150 0.1875 1.0% 0.050 0.100 0.2000.250 2.0% 0.100 0.200 0.400 0.500 3.0% 0.150 0.300 0.600 0.750 4.0%0.200 0.400 0.800 1.000 4.95% 0.2475 0.495 0.9904 1.2375 5.0% 0.2500.500 1.600 1.25 7.5% 0.375 0.750 1.500 1.875 10.0% 0.500 1.000 2.0002.500

In accordance with certain embodiments, for example, the nonwoven fabricmay have a basis weight from about 7 grams per square meter (gsm) toabout 150 gsm. In other embodiments, for instance, the fabric may have abasis weight from about 8 gsm to about 70 gsm. In certain embodiments,for example, the fabric may comprise a basis weight from about 10 gsm toabout 50 gsm. In further embodiments, for instance, the fabric may havea basis weight from about 11 gsm to about 30 gsm. As such, in certainembodiments, the fabric may have a basis weight from at least about anyof the following: 7, 8, 9, 10, and 11 gsm and/or at most about 150, 100,70, 60, 50, 40, and 30 gsm (e.g., about 9-60 gsm, about 11-40 gsm,etc.).

Moreover, fabrics prepared in accordance with embodiments of theinvention may be characterized by an area shrinkage of less than 5%. Infurther embodiments, for example, the fabrics may be characterized by anarea shrinkage of less than 2%.

According to certain embodiments, for example, the fibers may have alinear mass density from about 1 dtex to about 5 dtex. In otherembodiments, for instance, the fibers may have a dtex from about 1.5dtex to about 3 dtex. In further embodiments, for example, the fibersmay have a linear mass density from about 1.6 dtex to about 2.5 dtex. Assuch, in certain embodiments, the fibers have a linear mass density fromat least about any of the following: 1, 1.1, 1.2, 1.3, 1.4, 1.5, and 1.6dtex and/or at most about 5, 4.5, 4, 3.5, 3, and 2.5 dtex (e.g., about1.4-4.5 dtex, about 1.6-3 dtex, etc.).

Advantageously, the inventors of the present invention have discoveredthat the addition of the secondary alkane sulfonate in the PLA resinprovides significant increases in mechanical properties in comparison toan identical or similarly prepared nonwoven fabric that does not includethe secondary alkane sulfonate. In this regard, nonwoven fabrics inaccordance with embodiments of the present invention may exhibit tensilestrengths that are 50% greater in comparison to a similarly preparednonwoven fabric that does not include the secondary alkane sulfonate. Insome embodiments, the nonwoven fabric may exhibit a tensile strengththat is from 50% to 200% greater than the tensile strength of asimilarly prepared nonwoven fabric that does not include the secondaryalkane sulfonate.

In particular, nonwoven fabrics in accordance with the present inventionmay exhibit increases in machine direction (MD) tensile strengths thatare from about 55 to 125% in comparison to a similarly prepared nonwovenfabric that does not include the secondary alkane sulfonate. In someembodiments, the inventive nonwoven fabrics may exhibit an increase inMD tensile strength ranging from about 50 to 150%, such as from about 55to 125%, from about 65 to 110%, from about 85 to 110%, or from about 90to 110%, in comparison to a similarly prepared nonwoven fabric that doesnot include the secondary alkane sulfonate.

In some embodiments, nonwoven fabrics in accordance with the presentinvention may exhibit increases in cross direction (CD) tensilestrengths that are from about 50 to 200% in comparison to a similarlyprepared nonwoven fabric that does not include the secondary alkanesulfonate. In some embodiments, the inventive nonwoven fabrics mayexhibit an increase in CD tensile strength ranging from about 50 to170%, such as from about 55 to 165%, from about 65 to 160%, from about85 to 150%, or from about 90 to 125%, in comparison to a similarlyprepared nonwoven fabric that does not include the secondary alkanesulfonate.

Nonwoven fabrics in accordance with embodiments of the present inventionalso exhibit increased toughness in comparison to a similarly preparednonwoven fabric that does not include the secondary alkane sulfonate.The toughness of nonwoven fabrics may be compared by examining theproduct resulting from the multiplication of the observed percentelongation and the observed tensile strength of the fabric. The productof this multiplication is referred to as the Index of Toughness, whichis approximately proportional to the area under the stress strain curve.As discussed below in the Test Methods section, all tensile andelongation values are obtained according to German Method 10 DIN 53857in which a sample having a width of 5 cm and a 100 mm gauge length at across-head speed of 200 mm/min were recorded at peak. Since Index ofToughness results from the product of multiplying Tensile X %Elongation, the Index of Toughness has units of (N/5 cm)-%. Since allmechanical properties result from testing a 5 cm wide sample, the unitsfor Index of Toughness in this document will be simplified to N-%.

Nonwoven fabrics in accordance with the present invention may exhibit anMD Index of Toughness that is from about 2,000 to 7,500 N-%, and inparticular, from about 2,300 to 6,500, and more particularly, from about2,300 to 6,000 N-%, and a CD Index of Toughness that is from about 1,000to 5,000 N-%, and in particular, from about 1,250 to 5,000, and moreparticularly, from about 1,250 to 3,500 N-%.

In one embodiment, the inventive nonwoven fabric may exhibit an increasein MD Index of Toughness that is from 20 to 1,250% in comparison to asimilarly prepared nonwoven fabric that does not include the secondaryalkane sulfonate. For example, the inventive nonwoven fabric may exhibitan increase in MD Index of Toughness of any one or more of at least 25%,at least 100%, at least 200%, at least 300%, at least 400%, at least500%, at least 600%, at least 700%, at least 800%, at least 900%, atleast 1,000%, at least 1,050%, at least 1,100%, at least 1,150%, atleast 1,200%, at least 1,250%, at least 1,300%, or at least 1,500%, incomparison to a similarly prepared nonwoven fabric that does not includethe secondary alkane sulfonate.

In some embodiments, the inventive nonwoven fabric may exhibit anincrease in CD Index of Toughness that is from about 50 to 1,000% incomparison to a similarly prepared nonwoven fabric that does not includethe secondary alkane sulfonate. For example, the inventive nonwovenfabric may exhibit an increase in CD Index of Toughness of any one ormore of at least 60%, at least 75%, at least 80%, at least 85%, at least90%, at least 100%, at least 150%, at least 200%, at least 250%, atleast 300%, at least 350%, at least 400%, at least 500%, at least 550%,at least 600%, at least 700%, at least 800%, at least 900%, at least1,000%, or at least 1,025%, in comparison to a similarly preparednonwoven fabric that does not include the secondary alkane sulfonate.

To account for variations in basis weights, it may also be useful toconsider Relative Index of Toughness for the inventive nonwoven fabricsin comparison to similarly prepared nonwoven fabrics that do not includethe secondary alkane sulfonate. The inventive nonwoven fabrics alsoexhibited significant increases in toughness in comparison to thenonwoven fabrics of the comparative examples. The Relative Index ofToughness is calculated from the Index of Toughness, which is thennormalized for basis weight. The Toughness Index can be divided by basisweight to provide a normalized Index of Toughness with units ofN-%/g/m².

Nonwoven fabrics in accordance with the present invention may exhibit anMD Relative Index of Toughness that is from about 50 to 150 N-%/g/m²,and in particular, from about 75 to 125, and more particularly, fromabout 85 to 115 N-%/g/m², and a CD Relative Index of Toughness that isfrom about 40 to 100 N-%/g/m², and in particular, from about 45 to 85,and more particularly, from about 45 to 75 N-%/g/m².

In one embodiment, the inventive nonwoven fabric may exhibit an increasein MD Relative Index of Toughness that is from 100 to 1000% incomparison to a similarly prepared nonwoven fabric that does not includethe secondary alkane sulfonate. In a preferred embodiment, the inventivenonwoven fabric may exhibit an increase in MD Relative Index ofToughness that is from about 80 to 500%, and more preferably, from about140 to 480% in comparison to a similarly prepared nonwoven fabric thatdoes not include the secondary alkane sulfonate. For example, theinventive nonwoven fabric may exhibit an increase in MD Relative Indexof Toughness of any one or more of at least 100%, at least 125%, atleast 150%, at least 175%, at least 200%, at least 225%, at least 250%,at least 275%, at least 300%, at least 325%, at least 350%, at least375%, at least 400%, at least 425%, at least 450%, at least 475%, atleast 500%, at least 525%, at least 550%, at least 575%, at least 600%,at least 625%, at least 650%, at 675%, at least 700%, at least 725%, atleast 750%, at least 775%, at least 800%, at least 825%, at least 850%,at least 875%, at least 900%, at least 925%, at least 950, at least975%, or at least 1,000%, in comparison to a similarly prepared nonwovenfabric that does not include the secondary alkane sulfonate.

In one embodiment, the inventive nonwoven fabric may exhibit an increasein CD Relative Index of Toughness that is from 100 to 1000% incomparison to a similarly prepared nonwoven fabric that does not includethe secondary alkane sulfonate. In a preferred embodiment, the inventivenonwoven fabric may exhibit an increase in CD Relative Index ofToughness that is from about 140 to 500%, and more preferably, fromabout 140 to 410% in comparison to a similarly prepared nonwoven fabricthat does not include the secondary alkane sulfonate. For example, theinventive nonwoven fabric may exhibit an increase in MD Relative Indexof Toughness of any one or more of at least 100%, at least 125%, atleast 150%, at least 175%, at least 200%, at least 225%, at least 250%,at least 275%, at least 300%, at least 325%, at least 350%, at least375%, at least 400%, at least 425%, at least 450%, at least 475%, atleast 500%, at least 525%, at least 550%, at least 575%, at least 600%,at least 625%, at least 650%, at 675%, at least 700%, at least 725%, atleast 750%, at least 775%, at least 800%, at least 825%, at least 850%,at least 875%, at least 900%, at least 925%, at least 950, at least975%, or at least 1,000%, in comparison to a similarly prepared nonwovenfabric that does not include the secondary alkane sulfonate.

When comparing properties of different nonwovens it is often useful tocompare the root mean square of the combined values of the MD and CDproperty of interest. This method allows comparison of single values.The root mean square provides a single number that combines input fromboth the MD and the CD values by taking the square root of the sum ofthe square of the MD value plus the square of the CD value. Use of theroot mean square method to combine the MD and the CD results isparticularly useful if samples to be compared were made on differentmachines or under some different condition that might influence theMD/CD ratio. The root mean square of the Toughness Index per basisweight is calculated with the following formula:

$\left( \sqrt{\frac{({MDTI})^{2} + ({CDTI})^{2}}{2}} \right)\text{/}{Basis}\mspace{14mu}{weight}$Where MDTI is the machine direction Toughness Index and CDTI is thecross direction Toughness Index.

Nonwoven fabrics in accordance with the invention may have a root meansquare of the Toughness Index per basis weight that is at least 55N-%/g/m², and more preferably, at least 65 N-%/g/m², and even morepreferably at least 70 N-%/g/m². In one embodiment, the fabric has aroot mean square of the Toughness Index per basis weight has a valuefrom about 55 to 250 N-%/g/m², and in particular, from about 65 to 150N-%/g/m², and more particularly, from about 65 to 100 N-%/g/m². In oneembodiment, the fabric has a root mean square of the Toughness Index perbasis weight of at least 75, at least 80, at least 85, at least 90, atleast 95, at least 100, at least 105, at least 110, at least 115, atleast, 120, at least 125, at least, 130, at least 135, at least 140, atleast 145, at least 150, at least 155, at least 160, at least 165, atleast 170, at least 175, at least 180, at least 185, at least 190, atleast 195, and at least 200 N-%/g/m².

By “similarly prepared nonwoven fabric” it should be understood thecomparison nonwoven fabric has the identical polymer composition withthe exception of the secondary alkane sulfonate, and that slightvariations in processing conditions, such as temperature (e.g.,extruder, calendaring, and die temperatures), draw speeds, and pressuresmay exist.

While not wishing to be bound by theory, it is believed that thepresence of the secondary alkane sulfonate in the fibers may helpimprove bonding of fibers to each other, which results in improvementsin the mechanical properties of the nonwoven fabric. In this regard,FIGS. 1A and 1B are SEM images of a nonwoven fabric taken at amagnification of 250× and 100×, respectively, and FIGS. 2A and 2B areSEM images of an nonwoven fabric in accordance with the presentinvention taken at a magnification of 250× and 100×, respectively. Thefabric of FIGS. 1A and 1B are identical to the fabric of FIGS. 2A and 2Bwith the exception that the fabric of FIGS. 1A and 1B do not include asecondary alkane sulfonate. In both fabric, the fabric were point bondedwith a calender roll.

The SEM images of the fabric of FIGS. 1A and 1B show that the individualfibers of the bond points were poorly bonded to each other. Morespecifically, it is observed that the fibers exhibited relatively poormelting and flowing of the polymer during bonding. In contrast, the SEMimages of the fabric of FIGS. 2A and 2B exhibited good melting and flowof the polymer within each bond point. As can be seen in FIG. 2B, thisresulted in each bond point exhibiting a film like appearance due to themelting and flowing of the polymer. The inventive fabric exhibitedsignificant improvements in bonding in comparison to the fabric that didnot include the secondary alkane sulfonate.

According to certain embodiments, for instance, the fabric may comprisea machine direction (MD) tensile strength at peak from about 25 N/5 cmto about 150 N/5 cm. In other embodiments, for example, the fabric maycomprise a MD tensile strength at peak from about 50 N/5 cm to about 150N/5 cm. In further embodiments, for instance, the fabric may comprise aMD tensile strength at peak from about 65 N/5 cm to about 90 N/5 cm. Assuch, in certain embodiments the fabric may comprise a MD tensilestrength at peak from at least about any of the following: 25, 26, 27,28, 29, 30, 50, 60, 70, 80, 100, 110, 120, 130 N/5 cm, and 140/5 cm,and/or at most about 175, 150, 145, 140, 130, 120 N/5 cm, and 110, 100,and 90 N/5 cm (e.g., about 25-175 N/5 cm, about 80-140 N/5 cm, etc.).

In certain embodiments, for example, the fabric may comprise a crossmachine direction (CD) tensile strength at peak from about 20 N/5 cm toabout 85 N/5 cm. In other embodiments, for instance, the fabric maycomprise a CD tensile strength at peak from about 25 N/5 cm to about 75N/5 cm. In some embodiments, for example, the fabric may comprise a CDtensile strength at peak from about 29 N/5 cm to about 74 N/5 cm. Assuch, in certain embodiments, the fabric may comprise a CD tensilestrength at peak from at least about any of the following: 20, 21, 22,23, 24, 25, 26, 27, 28, 29, and 30 N/5 cm and/or at most about 85, 80,75, 70, 65, 60, and 50 N/5 cm (e.g., about 20-85 N/5 cm, about 25-75 N/5cm, etc.).

According to certain embodiments, for instance, the fabric may comprisean MD elongation percentage at peak from about 20% to about 50%. Inother embodiments, for example, the fabric may comprise an MD elongationpercentage at peak from about 25% to about 45%. In further embodiments,for instance, the fabric may comprise an MD elongation percentage atpeak from about 28% to about 41%. As such, in certain embodiments, thefabric may comprise an MD elongation percentage at peak from at leastabout any of the following: 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30,31, 32, 33, 34, 35, 36, 37, 38, 39, and 40% and/or at most about 50, 45,44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, 31, and 30% (e.g.,about 20-50%, about 21-45%, etc.).

In certain embodiments, for example, the fabric may comprise a CDelongation percentage at peak from about 30% to about 75%. In otherembodiments, for instance, the fabric may comprise a CD elongationpercentage at peak from about 35% to about 60%. In some embodiments, forexample, the fabric may comprise a CD elongation percentage at peak fromabout 40% to about 50%. As such, in certain embodiments, the fabric maycomprise an CD elongation percentage at peak from at least about any ofthe following: 10, 15, 20, 25, 30, 35, 36, 37, 38, 39, 40, 41, 42, 43,44, 45, 46, 47, 48, and 49% and/or at most about 55, 50, 49, 48, and 47%(e.g., about 10-55%, about 15-50%, etc.).

In accordance with certain embodiments, particular processes may be usedto prepare the PLA spunbond nonwoven fabrics. In such embodiments, theprocess may include providing a stream of molten or semi-molten PLAresin that includes at least one secondary alkane sulfonate, forming aplurality of drawn PLA continuous filaments, depositing the plurality ofPLA continuous filaments onto a collection surface, exposing theplurality of PLA continuous filaments to ions, and bonding the pluralityof PLA continuous filaments to form the PLA spunbond nonwoven fabric.According to certain embodiments, for example, forming the plurality ofPLA continuous filaments may comprise spinning the plurality of PLAcontinuous filaments, drawing the plurality of PLA continuous filaments,and randomizing the plurality of PLA continuous filaments.

In this regard, the spunbond nonwoven web may be produced, for example,by the conventional spunbond process wherein molten polymer is extrudedinto continuous filaments which are subsequently quenched, attenuated ordrawn mechanically by draw rolls or pneumatically by a high velocityfluid, and collected in random arrangement on a collecting surface.After filament collection, any thermal, chemical or mechanical bondingtreatment may be used to form a bonded web such that a coherent webstructure results.

In accordance with certain embodiments, for instance, the process mayoccur at a fiber draw speed greater than about 2500 m/min. In otherembodiments, for example, the process may occur at a fiber draw speedfrom about 3000 m/min to about 4000 m/min. In further embodiments, forinstance, the process may occur at a fiber draw speed from about 3000m/min to about 5500 m/min. As such, in certain embodiments, the processmay occur at a fiber draw speed from at least about any of thefollowing: 2501, 2550, 2600, 2650, 2700, 2750, 2800, 2850, 2900, 2950,and 3000 m/min and/or at most about 5500, 4000, 3950, 3900, 3850, 3800,3750, 3700, 3650, 3600, 3550, and 3500 m/min (e.g., about 2700-3800m/min, about 3000-3700 m/min, etc.).

In accordance with certain embodiments, for instance, bonding the web toform the PLA spunbond nonwoven fabric may comprise thermal point bondingthe web with heat and pressure via a calender having a pair ofcooperating rolls including a patterned roll. In such embodiments, forexample, thermal point bonding the web may comprise imparting athree-dimensional geometric bonding pattern onto the PLA spunbondnonwoven fabric. The patterned roll may comprise a three-dimensionalgeometric bonding pattern. In some embodiments, for example, the bondingpattern at least one of a diamond pattern, a hexagonal dot pattern, anoval-elliptic pattern, a rod-shaped pattern, or any combination thereof.In some embodiments, the calender may include a release coating tominimize deposit of molten or semi molten polymer on the surface of oneor more of the rolls. As an example, such release coating is describedin European Patent Application No. 1,432,860, which is incorporatedherein in its entirety by reference.

In accordance with certain embodiments, for instance, the process mayfurther comprise dissipating static charge from the PLA spunbondnonwoven fabric proximate to the calender via the static control unit.In some embodiments, for example, the static control unit may comprisean ionization source. In further embodiments, for instance, theionization source may comprise an ionization bar. However, in otherembodiments, for example, dissipating static charge from the PLAspunbond nonwoven fabric may comprise contacting the PLA spunbondnonwoven fabric with a static bar.

In accordance with certain embodiments, for instance, the process mayfurther comprise cutting the PLA spunbond nonwoven fabric to form cutPLA spunbond nonwoven fabric, exposing the cut PLA spunbond nonwovenfabric to ions via a third ionization source, and winding the cut PLAspunbond nonwoven fabric into rolls. In such embodiments, for example,the third ionization source may comprise an ionization bar.

In accordance with certain embodiments, for instance, the process mayfurther comprise increasing humidity while forming the plurality of PLAcontinuous filaments. In such embodiments, for example, increasinghumidity may comprise applying at least one of steam, fog, mist, or anycombination thereof to the plurality of PLA continuous filaments.

Certain embodiments according to the invention provide systems forpreparing a PLA spunbond nonwoven fabric. In accordance with certainembodiments, the system includes a first PLA source configured toprovide a stream of molten or semi-molten PLA resin, a source of atleast one secondary alkane sulfonate that is configured to introduce theat least one secondary alkane sulfonate into the PLA source, a spin beamin fluid communication with the first PLA source, a collection surfacedisposed below an outlet of the spin beam onto which the PLA continuousfilaments are deposited to form the PLA spunbond nonwoven fabric, afirst ionization source positioned and arranged to expose the PLAcontinuous filaments to ions, and a calender positioned downstream ofthe first ionization source. The spin beam, according to certainembodiments, is configured to extrude and draw a plurality of PLAcontinuous filaments.

In this regard, the spunbond nonwoven web may be produced, for example,by the conventional spunbond process on spunbond machinery such as, forexample, the Reicofil-3 line or Reicofil-4 line from Reifenhauser, asdescribed in U.S. Pat. No. 5,814,349 to Geus et al, the entire contentsof which are incorporated herein by reference, wherein molten polymer isextruded into continuous filaments which are subsequently quenched,attenuated pneumatically by a high velocity fluid, and collected inrandom arrangement on a collecting surface. In some embodiments, thecontinuous filaments are collected with the aid of a vacuum sourcepositioned below the collection surface. After filament collection, anythermal, chemical or mechanical bonding treatment may be used to form abonded web such that a coherent web structure results. As one skilled inthe art will understand, examples of thermal bonding may includethru-air bonding where hot air is forced through the web to soften thepolymer on the outside of certain fibers in the web followed by at leastlimited compression of the web or calender bonding where the web iscompressed between two rolls, at least one of which is heated, andtypically one is an embossed roll.

In some embodiments, for instance, the collection surface may compriseconductive fibers. The conductive fibers may comprise monofilament wiresmade from polyethersulfone conditioned with polyamide (e.g., Huycon— LX135). In the machine direction, the fibers comprise polyamideconditioned polyethersulfone. In the cross-machine direction, the fiberscomprise polyamide conditioned polyethersulfone in combination withadditional polyethersulfone.

With reference to FIG. 3 , for example, a schematic diagram of the PLAspunbond nonwoven fabric preparation system in accordance with certainembodiments of the invention is illustrated.

As shown in FIG. 3 , a PLA source (i.e. hopper) 2 is in fluidcommunication with the spin beam 4 via the extruder 6. At least onesecondary alkane sulfonate is then blended with PLA resin in theextruder 6 to provide a molten or semi-molten PLA stream that isintroduced into the spin beam 4. It should be noted that the secondaryalkane sulfonate may be introduced directly into the extruder or may beintroduced into the PLA source (e.g., the hopper) prior to the PLA resinbeing introduced into the extruder.

Although FIG. 3 illustrates an embodiment having two PLA sources 2 andtwo extruders 6, the system may include any number of polymer sources(e.g., PLA, synthetic polymer, such as polypropylene, polyethylene,etc.) and extruders as dictated by a particular application asunderstood by one of ordinary skill in the art. Following extrusion, theextruded polymer may then enter a plurality of spinnerets (not shown)for spinning into filaments. Following spinning, the spun filaments maythen be drawn (i.e. attenuated) via a drawing unit (not shown) andrandomized in a diffuser (28 in FIGS. 4A-4C). The spin beam 4 produces acurtain of filaments (30 in FIGS. 4A-4C) that is deposited on thecollection surface 10 at point 8.

In one embodiment, the thus deposited filaments may then be bonded toform a coherent web. In some embodiments, a pair of cooperating rolls 12(also referred to herein as a “press roll”) stabilize the web of the PLAcontinuous filaments by compressing the web before delivery to thecalender 14 for bonding. In some embodiments, for example, the pressroll may include a ceramic coating deposited on a surface thereof. Incertain embodiments, for instance, one roll of the pair of cooperatingrolls 12 may be positioned above the collection surface 10, and a secondroll of the pair of cooperating rolls 12 may be positioned below thecollection surface 10. Finally, the bonded PLA spunbond nonwoven fabricmoves to a winder 16, where the fabric is wound onto rolls.

During the course of their investigation, the inventors have discoveredthat static generation during fiber spinning and web processing when PLAis exposed on the fiber surface promotes web wraps at the press rollsand calender of the spunbond machine. This web wrap is undesirable andgenerally has prevented the high speed production of fabrics comprising100% PLA, or fabrics in which PLA is exposed at the surface of thefibers. One method of addressing web wrap is by increasing the humidityof the spunbond process by, for example, injecting steam into the airstream used to quench the just-spun fibers or providing a fine mist orfog of moisture around the press rolls where the spun fibers are firstformed into an unbonded web. Although the extra humidity provides someprotection from web wraps, the addition of high moisture over a periodof time may promote corrosion of the spunbond machine and growth of moldor microorganisms detrimental to nonwoven use in hygiene and medicaloperations.

Another method of reducing static charge build up in the nonwoven fabricis to contact the web where the PLA is exposed on the surface of thefiber with a conductive static bar, which helps to ground the web,thereby dissipating charge build-up. However, this approach requiresdirect contact between the nonwoven web and the conductive substrate,and at such contact points there remains the possibility of directdischarge of static electricity through space with resulting possibleharm to the operator, damage to equipment and risk of fire.

Advantageously, the inventors have discovered that fabrics comprising100% PLA may be prepared at commercially viable processing speeds bypositioning one or more ionization sources in close proximity to thenonwoven fabric. For example, in one embodiment, an ionization source 18may be positioned near the spin beam 4 and the winder 16 to activelydissipate/neutralize static charge without contacting the fabric. Asexplained below, the ionization source exposes the nonwoven fabric to astream of ions, which act to neutralize static charges in the nonwovenfabric. The stream of ions may include positive ions, negative ions, andcombinations thereof.

In some embodiments, it may also be desirable to position a staticcontrol unit 20 near the calender 14. The static control unit 20 may bea passive static bar requiring contact with the fabric or an activeionization bar, which does not require contact with the fabric. Finally,an optional humidity unit 26 may be used in conjunction with the spinbeam 4 and/or the press roll 12 to reduce static via added moisture.

In accordance with certain embodiments, for example, the firstionization source may be positioned above the collection surface anddownstream of a point at where the PLA continuous filaments aredeposited on the collection surface. However, in other embodiments, forinstance, the first ionization source may be positioned between theoutlet of the spin beam and the collection surface.

As discussed previously, the system may further comprise a press rollpositioned downstream from the outlet of the spin beam. In this regard,the press roll may be configured to stabilize the web of the PLAcontinuous filaments by compressing said web before delivery of the PLAcontinuous fibers from the outlet of the spin beam towards the calender.In those embodiments including the press roll, for example, the firstionization source may be positioned downstream from the press roll. Inother embodiments, for instance, the first ionization source may bepositioned between the spin beam and the press roll.

In some embodiments and as shown in FIG. 3 , the system may comprise avacuum source 24 disposed below the collection surface for pulling theplurality of PLA continuous filaments from the outlet of the spin beamonto the collection surface before delivery to the calender.

FIGS. 4A-4C, for example, are schematic diagrams illustratingpositioning of the first ionization source in accordance with certainembodiments of the invention. As shown in FIG. 4A, the first ionizationsource 18 is positioned downstream of the outlet (i.e. diffuser) 28 ofthe spin beam 4 but upstream of the press roll 12. In FIG. 4B, however,the first ionization source 26 is positioned downstream of the pressroll 12. In FIG. 2C, the first ionization source is positioneddownstream of the point 8 at which the curtain of filaments 30 aredeposited on the collection surface but also within the outlet 46.

Preferably, the ionization source comprises a device that is capable ofactively discharging ions with the use of electrodes, ionizing airnozzles, ionizing air blowers, and the like. In one embodiment, theionization source comprises an active discharge ionization bar thatactively discharges ions in the direction of the nonwoven fabric.Examples of suitable ionization bars may include ElektrostatikDischarging Electrode E3412, which is available from Iontis.

In one embodiment, the ionization bar may extend over the web in thecross direction. Preferably, the ionization bar extends in the crossdirection across the total width of the nonwoven fabric. In furtherembodiments, the ionization bar may extend under the web and thecollection surface in the cross direction. However, positioning theionization bar under the collection surface may be less effective thanpositioning the ionization bar over the web in the cross direction.

According to certain embodiments, for example, the first ionizationsource and the collection surface may be separated by a distance fromabout 1 inch to about 24 inches. In other embodiments, for instance, thefirst ionization source and the collection surface may be separated by adistance from about 1 inch to about 12 inches. In further embodiments,for example, the first ionization source and the collection surface maybe separated by a distance from about 1 inch to about 5 inches. As such,in certain embodiments, the first ionization source and the collectionsurface may be separated by a distance from at least about any of thefollowing: 1, 1.25, 1.5, 1.75, and 2 inches and/or at most about 24, 20,16, 12, 10, 9, 8, 7, 6, and 5 inches (e.g., about 1.5-10 inches, about2-8 inches, etc.).

In accordance with certain embodiments, for instance, the system mayfurther comprise a static control unit positioned and arranged todissipate static from the PLA spunbond nonwoven fabric proximate to thecalender. In some embodiments, for example, the static control unit maybe positioned upstream from, and adjacent to, the calender. In otherembodiments, however, the static control unit may be positioneddownstream from, and adjacent to, the calender.

In some embodiments, for instance, the static control unit may comprisea passive static bar. In such embodiments, the static control unit maycontact the PLA spunbond nonwoven fabric in order to dissipate staticcharge. In other embodiments, however, the static control unit maycomprise a second ionization source. As such, the second ionizationsource may actively dissipate static charge from the PLA spunbondnonwoven fabric such that contact by the second ionization source withthe PLA spunbond nonwoven fabric is not required in order to dissipatethe static charge.

According to certain embodiments, for example, the system may furthercomprise a winder positioned downstream from the calender. In suchembodiments, for instance, the system may also include a thirdionization source positioned and arranged to expose the PLA spunbondnonwoven fabric to ions proximate to the winder. In some embodiments,for example, at least one of the first ionization source, the staticcontrol source (e.g., the second ionization source), and the thirdionization source may comprise an ionization bar. In this regard, forinstance, the first ionization source, the static control source, andthe third ionization source may be configured to actively dissipatestatic charge created during preparation of the PLA spunbond nonwovenfabric.

In accordance with certain embodiments, for example, the system mayfurther comprise a humidity unit positioned within or downstream fromthe spin beam. In such embodiments, for instance, the humidity unit maycomprise at least one of a steam unit, a fogging unit, a misting unit,or any combination thereof. In this regard, for example, humidity may beadded in the spin beam during the formation of the plurality of PLAcontinuous filaments and/or near the press roll(s) (in those embodimentsutilizing at least one press roll) in order to provide additionalmanagement of static charge that develops during the production of thePLA spunbond nonwoven fabric.

Nonwoven fabrics in accordance with embodiments of the invention may beused to prepare a variety of different structures. For example, in someembodiments, the inventive nonwoven fabric may be combined with one ormore additional layers to prepare a composite or laminate material.Examples of such composites/laminates may include a spunbond composite,a spunbond-meltblown (SM) composite, a spunbond-meltblown-spunbond (SMS)composite, or a spunbond-meltblown-meltblown-spunbond (SMMS) composite.In some embodiments, composites may be prepared comprising a layer ofthe inventive nonwoven fabric and one or more film layers.

For example, FIGS. 5A-5D are cross-sectional views of composites inaccordance with certain embodiments of the invention. For example, FIG.5A illustrates a spunbond-meltblown (SM) composite 50 having a PLAspunbond nonwoven fabric layer 52 in accordance with embodiments of thepresent invention, and a meltblown layer 54. FIG. 5B illustrates aspunbond-meltblown-spunbond (SMS) composite 56 having two PLA spunbondnonwoven fabric layers 52 and a meltblown layer 54 sandwiched betweenthe PLA spunbond nonwoven fabric layers 52. FIG. 5C illustrates an SMScomposite 58 having a PLA spunbond nonwoven fabric layer 52, a differentspunbond layer 60, and a meltblown layer 54 sandwiched between the twospunbond layers 52, 6. Finally, FIG. 4D illustrates aspunbond-meltblown-meltblown-spunbond (SMMS) composite 62 having a PLAspunbond nonwoven fabric layer 52, a different spunbond layer 60, andtwo meltblown layers 54 sandwiched between the two spunbond layers 52,60. Although the SMMS composite 62 is shown as having two differentspunbond layers 52 and 60, both spunbond layers may be the PLA spunbondnonwoven fabric layer 52.

In these multilayer structures, the basis weight of the PLA spunbondnonwoven fabric layer may range from as low as 7 g/m² and up to 150g/m². In such multilayered laminates, both the meltblown and spunbondfibers could have PLA on the surface to insure optimum bonding. In someembodiments in which the spunbond layer is a part of a multilayerstructure (e.g., SM, SMS, and SMMS), the amount of the meltblown in thestructure may range from about 5 to 30%, and in particular, from about 5to 15% of the structure as a percentage of the structure as a whole.

Multilayer structures in accordance with embodiments can be prepared ina variety of manners including continuous in-line processes where eachlayer is prepared in successive order on the same line, or depositing ameltblown layer on a previously formed spunbond layer. The layers of themultilayer structure can be bonded together to form a multilayercomposite sheet material using thermal bonding, mechanical bonding,adhesive bonding, hydroentangling, or combinations of these. In certainembodiments, the layers are thermally point bonded to each other bypassing the multilayer structure through a pair of calender rolls.

In yet another aspect, certain embodiments of the invention provideabsorbent articles. In accordance with certain embodiments, theabsorbent article may include a nonwoven fabric in accordance with thepresent invention. In one embodiment, a sustainable composite may beprovided that includes at least two nonwoven fabric layers such that atleast one nonwoven fabric layer may comprise a PLA spunbond nonwovenfabric layer in which a secondary alkane sulfonate is incorporated. ThePLA spunbond nonwoven fabric layer may comprise a plurality of fiberssuch that PLA may be present at a surface of the plurality of fibers. Insome embodiments, the absorbent article may be sustainable, but thesustainability of the absorbent article depends upon the other materialsincorporated into the absorbent article other than the sustainablecomposite.

In this regard, fabrics prepared in accordance with embodiments of theinvention may be used in wide variety of articles and applications. Forinstance, embodiments of the invention may be used for personal careapplications, for example products for babycare (diapers, wipes), forfemcare (pads, sanitary towels, tampons), for adult care (incontinenceproducts), or for cosmetic applications (pads), agriculturalapplications, for example root wraps, seed bags, crop covers, industrialapplications, for example work wear coveralls, airline pillows,automobile trunk liners, sound proofing, and household products, forexample mattress coil covers and furniture scratch pads.

FIG. 6A, for example, is an illustration of an absorbent article (shownhere as a diaper) in accordance with at least one embodiment of theinvention and broadly designated by reference numeral 70. The diaper 70may include an absorbent core 74. FIG. 6B is a cross-sectional view ofthe diaper 70 of FIG. 5A taken along line 72-72 of FIG. 5A. As shown inFIG. 6B, the absorbent core 74 may be sandwiched between a topsheet 80and a backsheet 82. As further discussed herein, one or both of thetopsheet 80 and the backsheet 82 may comprise a PLA spunbond nonwovenfabric and/or a sustainable composite including a PLA spunbond nonwovenfabric layer as previously discussed in more detail herein.

The topsheet 30 is positioned adjacent an outer surface of the absorbentcore 74 and is preferably joined thereto and to the backsheet 82 byattachment means (not shown) such as those well known in the art. Forexample, the topsheet 80 may be secured to the absorbent core 74 by auniform continuous layer of adhesive, a patterned layer of adhesive, oran array of separate lines, spirals, or spots of adhesive.

As used herein, the term “joined” encompasses configurations whereby anelement is directly secured to the other element by affixing the elementdirectly to the other element, and configurations whereby the element isindirectly secured to the other element by affixing the element tointermediate member(s) which in turn are affixed to the other element.In a preferred embodiment of the present invention, the topsheet 80 andthe backsheet 82 are joined directly to each other in the diaperperiphery 86 and are indirectly joined together by directly joining themto the absorbent core 74 by the attachment means (not shown).

Preferably, the topsheet 80 is compliant, soft feeling, andnon-irritating to the wearer's skin. Further, the topsheet 80 is liquidpervious permitting liquids (e.g., urine) to readily penetrate throughits thickness. A suitable topsheet may be manufactured from a wide rangeof materials, such as porous foams; reticulated foams; apertured plasticfilms; or woven or nonwoven webs of natural fibers (e.g., wood or cottonfibers), or a combination of natural and synthetic fibers.

In some embodiments, the topsheet may be treated with a surfactant tohelp ensure proper liquid transport through the topsheet and into theabsorbent core. An example of a suitable surfactant is available fromMomentive Performance Materials under the tradename NUWET™ 237.

In one embodiment, at least one of the topsheet and backsheet comprisesa nonwoven fabric comprising PLA continuous filaments that includes asecondary alkaline sulfonate as discussed previously.

In a preferred embodiment, the topsheet comprises at least 75 weightpercent of bio-based materials, such as at least 75 weight percent ofthe inventive PLA spunbond nonwoven fabric. Additional examples ofbio-based polymers that may be used in embodiments of the inventioninclude polymers directly produced from organisms, such aspolyhydroxyalkanoates (e.g., poly(beta-hydroxyalkanoate),poly(3-hydroxybutyrate-co-3-hydroxyvalerate, NODAX™), and bacterialcellulose; polymers extracted from plants and biomass, such aspolysaccharides and derivatives thereof (e.g., gums, cellulose,cellulose esters, chitin, chitosan, starch, chemically modified starch),proteins (e.g., zein, whey, gluten, collagen), lipids, lignins, andnatural rubber; and current polymers derived from naturally sourcedmonomers and derivatives, such as bio-polyethylene, bio-polypropylene,polytrimethylene terephthalate, polylactic acid, NYLON 11, alkyd resins,succinic acid-based polyesters, and bio-polyethylene terephthalate.

There are a number of manufacturing techniques which may be used tomanufacture the topsheet 80. For example, the topsheet 80 may be anonwoven web of fibers. When the topsheet comprises a nonwoven web, theweb may be spunbonded, carded, wet-laid, meltblown, hydroentangled,combinations of the above, or the like. A preferred topsheet comprises aspunbond nonwoven fabric in which the fibers are thermally bonded toeach other to form a coherent web.

The backsheet 82 is positioned adjacent to an opposite surface of theabsorbent core 74 and is preferably joined thereto by attachmentmechanisms (not shown) such as those well known in the art. Suitableattachment mechanisms are described with respect to joining the topsheet80 to the absorbent core 74. Alternatively, the attachment means maycomprise heat bonds, pressure bonds, ultrasonic bonds, dynamicmechanical bonds, or any other suitable attachment means or combinationsof these attachment mechanisms as are known in the art.

The backsheet 82 is impervious to liquids (e.g., urine) and ispreferably manufactured from a thin plastic film, although otherflexible liquid impervious materials may also be used. As used herein,the term “flexible” refers to materials which are compliant and willreadily conform to the general shape and contours of the human body. Thebacksheet 82 prevents the exudates absorbed and contained in theabsorbent core 74 from wetting articles which contact the diaper 70 suchas bedsheets and undergarments. The backsheet 82 may thus comprise awoven or nonwoven material, polymeric films such as thermoplastic films,or composite materials such as a film-coated nonwoven material.

In some embodiments, material for the backsheet may include thebio-based polymers discussed previously, and in particular, theinventive PLA spunbond fabric described herein. In some embodiments, thebacksheet may include additional bio-based polymers. For example,bio-based polymers for use in the backsheet may include polymersdirectly produced from organisms, such as polyhydroxyalkanoates (e.g.,poly(beta-hydroxyalkanoate),poly(3-hydroxybutyrate-co-3-hydroxyvalerate, NODAX™), and bacterialcellulose; polymers extracted from plants and biomass, such aspolysaccharides and derivatives thereof (e.g., gums, cellulose,cellulose esters, chitin, chitosan, starch, chemically modified starch),proteins (e.g., zein, whey, gluten, collagen), lipids, lignins, andnatural rubber; and current polymers derived from naturally sourcedmonomers and derivatives, such as bio-polyethylene, bio-polypropylene,polytrimethylene terephthalate, polylactic acid, NYLON 11, alkyd resins,succinic acid-based polyesters, and bio-polyethylene terephthalate.

In one embodiment, the backsheet may comprise a laminate structurehaving a liquid impervious film layer that is joined to a nonwoven web.Suitable films may be prepared from the bio-based polymers as previouslydiscussed. In one example, the film may comprise a sugar cane derivedpolyethylene polymer, such as a film grade LDPE polyethylene gradeSEB853/72 or SPB681/59 recommended by Braskem S. A. for lamination.Suitable films may also include additives such as CaCO₃ to improve filmbreathability while still maintaining fluid barrier properties. In someembodiments, the backsheet layer may comprise a laminate structurehaving a bio-based film layer, such as those discussed previously, thatis laminated to a fabric layer having a spunbond-meltblown-spunbond(SMS) structure.

The absorbent core 74 may comprise any material that is capable ofabsorbing fluids and exudates. Preferably, the absorbent core comprisesat least 75% by weight of bio-based materials. In one embodiment,materials for the core wrap may comprise a fabric layer comprising aspunbond fabric, spunbond-meltblown fabric (SM), or an SMS fabric. Anexample of a core wrap comprising an SMS fabric comprises a spunbondnonwoven layer comprising bicomponent fibers having a PLA sheath (e.g.,Nature Works PLA Grade PLA 6752 with 4% D Isomer), and a PLA core (e.g.NatureWorks Grade 6202 with 2% D Isomer). In one embodiment, themeltblown layer of the SMS fabric may be comprised of a PLA meltblownfibers (e.g., NatureWorks PLA grade 6252).

FIG. 7 is an illustration of an absorbent article in accordance with atleast one embodiment of the invention in which the absorbent article isin the form of a feminine sanitary pad broad designated by referencenumeral 100. Pad 100 may include a topsheet 102, backsheet 104, and anabsorbent core 106 disposed there between. Preferably, topsheet 102 andbacksheet 104 are joined to each other about along opposing outer edgesto define a continuous seam 108 that extends about the periphery 110 ofthe pad 100. Continuous seam 108 may comprise a heat seal that is formedfrom thermally bonding the topsheet and backsheet to each other. Inother embodiments, continuous seam 108 is formed by adhesively bondingthe topsheet and backsheet to each other.

As in the embodiments discussed above, pad 100 preferably comprises anonwoven fabric in accordance with the present invention. That is aspunbond nonwoven fabric comprising fibers that are a blend of a PLAresin and a secondary alkaline sulfonate.

In some embodiments, the pad 100 may comprise a sustainable articlescomprising a bio-based material content of at least 75 weight percent,based on the total weight of the pad, such as comprising a bio-basedmaterial content that is at least 80%, 85%, 90%, or 95% by weight of thepad. Suitable materials for the topsheet, backsheet, and absorbent coreare discussed previously.

In some embodiments, pad 100 may also include a fluid acquisition layer112 that is disposed between the absorbent core 106 and the topsheet102. In one embodiment a fluid acquisition layer could be made bycarding a web comprised of a blend of 7 denier hollow PLA-Type 820 2inch cut length staple fibers plus 3 denier Solid PLA—Type 821 2 inchcut length staple fibers, (both available from Fiber InnovationsTechnology—Johnson City, Tenn.); treating the resulting carded web viakiss roll with a suspension of cooked starch (for example type STABITEX65401 from Cargill); exposing the resulting web of fiber and starch toelevated temperature via a combination of hot air and contact to heateddryer cans to cure and dry the web, and winding and slitting theresulting roll in to child rolls for use in the absorbent article.

Various components of the absorbent article are typically joined viathermal or adhesive bonding. When an adhesive is employed, the adhesivepreferably comprises a bio-based adhesive. An example of a bio-basedadhesive is a pressure sensitive adhesive available from DanimerScientific under the product code 92721.

In accordance with certain embodiments, for example, at least the PLAspunbond nonwoven fabric layer may comprise bicomponent fibers. In someembodiments, for instance, the bicomponent fibers may comprise aside-by-side arrangement. However, in other embodiments, for example,the bicomponent fibers may comprise a sheath and a core. In furtherembodiments, for instance, the bicomponent fibers may comprise reversebicomponent fibers. In certain embodiments, for example, the sheath maycomprise PLA. In further embodiments, for instance, the core maycomprise at least one of a polyolefin, a polyester, or any combinationthereof. In some embodiments, for example, the core may comprise atleast one of a polypropylene, a polyethylene, a polyethyleneterephthalate, PLA, or any combination thereof. In certain embodiments,for instance, each of the sheath and the core may comprise PLA.

According to certain embodiments, for example, the sheath may comprise afirst PLA grade, the core may comprise a second PLA grade, and the firstPLA grade and the second PLA grade may be different. In someembodiments, for instance, the first PLA grade may comprise up to about5% crystallinity, and the second PLA grade may comprise from about 40%to about 50% crystallinity. In other embodiments, for example, the firstPLA grade may comprise a melting point from about 125° C. to about 135°C., and the second PLA grade may comprise a melting point from about155° C. to about 170° C. In further embodiments, for instance, the firstPLA grade may comprise a weight percent of D isomer from about 4 wt. %to about 10 wt. %, and the second PLA grade may comprise a weightpercent of D isomer of about 2 wt. %. In some embodiments, for example,the bicomponent fibers may comprise about 70 wt. % core and about 30 wt.% sheath.

However, in other embodiments, for instance, at least the PLA spunbondnonwoven fabric layer may comprise a plurality of monocomponent PLAfibers comprising a blend of a PLA resin and a secondary alkane sulfone.

In a preferred embodiment, the PLA nonwoven fabric in accordance withthe present invention may be used to manufacture sustainable absorbentarticles. Examples of sustainable absorbent articles may be found inU.S. patent application Ser. No. 14/839,026 to Chester et al.,incorporated fully by referenced herein.

In accordance with certain embodiments, for example, at least the PLAspunbond nonwoven fabric layer may comprise a three-dimensionalgeometric bonding pattern. In such embodiments, for instance, thebonding pattern may comprise at least one of a diamond pattern, ahexagonal dot pattern, an oval-elliptic pattern, a rod-shaped pattern,or any combination thereof.

EXAMPLES

The following examples are provided for illustrating one or moreembodiments of the present invention and should not be construed aslimiting the invention.

Nonwoven fabrics in accordance with the invention were prepared via aReifenhaeuser Reicofil-3 line or Reicofil-4 line. Each of the exampleswere prepared using the setup described in Example 1 unless otherwiseindicated. Moreover, unless otherwise indicated all percentages areweight percentages. The materials used in the examples are identifiedbelow.

Test Methods

Titer was calculated from microscopic measurement of fiber diameter andknown polymer density per German textile method C-1570.

Basis Weight was determined generally following the German textilemethod CM-130 from the weight of 10 layers of fabric cut into 10×10 cmsquares.

Tensile was determined in accordance with Method 10 DIN 53857 using asample with 5 cm width, 100 mm gauge length, and cross-head speed of 200mm/min. Tensile strengths were measured at peak.

Elongation was determined in accordance with Method 10 DIN 53857 using asample with 5 cm width, 100 mm gauge length, and cross-head speed of 200mm/min. Elongations were measured at peak.

Fabric Shrinkage was determined by cutting three samples taken acrossthe web width of nominal dimensions of MD of 29.7 cm and CD of 21.0 cm;measuring the actual MD and CD width at three locations in the sheet;placing the sample in water heated to 60° C. for 1 minute; andremeasuring the MD and CD dimensions at the above three locations. Theaverage width measurement after exposure divided by the originalmeasurement X 100% yielded the % Shrinkage. A low % shrinkage valuesuggests that the continuous fibers comprising PLA have been spun anddrawn at sufficient speed to yield after bonding a high strength stablefabric.

Comparative Examples 1, 2, and 3

In Comparative Examples 1, 2 and 3 a 100% PLA bicomponent fabric wasprepared on a Reicofil-4 beam. A press roll (R-4 press roll) waspositioned on the collection surface downstream of where the filamentsare deposited on the collection surface. An Ionis ElektrostatikDischarging Electrode E3412 (i.e. ionization bar) was positioned aboveand extending over the collection surface in the cross direction andplaced approximately 1 to 3 inches above the collection surface and 2 to3 inches downstream of the R-4 press roll.

The fabrics were bicomponent 30/70 NatureWorks Grade 6752/NatureWorksGrade 6202/sheath/core made with ionization bars positioned as discussedabove to minimize static. The fabrics of Comparative Examples 1, 2 and 3were produced at spin beam temperatures of 235° C. at the extruder and240° C. at the die. The fabric of Comparative Example 1 was produced ata fiber draw speed of 3600 m/min and a line speed of 145 m/min. Thecalender for Comparative Example 1 had calender temperatures of 160° C.for the pattern roll and 147° C. for the anvil roll and a calenderpressure of 40 N/mm.

The fabric of Comparative Example 2 was produced using a fiber drawspeed of 3800 m/min and a line speed of 90 m/min. The calender forCompaative Example 2 had calender temperatures of 160° C. for thepattern roll and 147° C. for the anvil roll and a calender pressure of40 N/mm.

The fabric of Comparative Example 3 was produced using a fiber drawspeed of 3200 m/min and a line speed of 145 m/min. The calender forComparative Example 3 had calender temperatures of 160° C. for thepattern roll and 147° C. for the anvil roll and a calender pressure of40 N/mm. Mechanical properties of Comparative Examples 1, 2, and 3 aresummarized in Tables 4 and 5 below.

Inventive Example 1

In Inventive Example 1, a 100% PLA bicomponent fabric having asheath/core structure was prepared in which 2 weight percent of amasterbatch comprising a PLA resin and a secondary alkane sulfonate wasadded to the polymer component defining the sheath. The setup of thesystem is the same as described above for Comparative Examples 1, 2, and3.

The fabric was a bicomponent 30/70 NatureWorks Grade 6752/NatureWorksGrade 6202/sheath/core made with ionization bars as discussed above tominimize static. At the sheath extruder, 2% by weight of a masterbatchof Sukano Antistatic Product S 546 was combined with NatureWorks Grade6752 to provide the sheath of the bicomponent fibers. BICO. The fabricof Inventive Example 1 was produced at spin beam temperatures of 235° C.at the extruder and 240° C. at the die. The fabric of Inventive Example1 was produced at a fiber draw speed of 3800 m/min and a line speed of145 m/min. The calender for Inventive Example 1 had calendertemperatures of 160° C. for the pattern roll and 147° C. for the anvilroll and a calender pressure of 40 N/mm. Properties of Inventive Example1 are summarized in Tables 4 and 5 below.

Inventive Example 2

In Inventive Example 2, a 100% PLA bicomponent fabric having asheath/core arrangement was prepared in which 3 weight percent of amasterbatch comprising a PLA resin and a secondary alkane sulfonate wasadded to the polymer component defining the sheath. The setup of thesystem is the same as described above for Comparative Examples 1, 2, and3.

The fabric was a bicomponent 30/70 NatureWorks Grade 6752/NatureWorksGrade 6202/sheath/core made with ionization bars as discussed above tominimize static. At the sheath extruder, 3% by weight of a masterbatchof Sukano Antistatic Product S 546 was combined with NatureWorks Grade6752 to provide the sheath of BICO Example 12. The fabric of InventiveExample 2 was produced at spin beam temperatures of 235° C. at theextruder and 240° C. at the die. The fabric of Inventive Example 2 wasproduced at a fiber draw speed of 3550 m/min and a line speed of 145m/min. The calender for Inventive Example 2 had calender temperatures of160° C. for the pattern roll and 147° C. for the anvil roll and acalender pressure of 40 N/mm. Properties of Inventive Example 2 aresummarized in Tables 4 and 5 below.

Inventive Example 3

In Inventive Example 3, a 100% PLA bicomponent fabric having asheath/core arrangement was prepared in which 2 weight percent of amasterbatch comprising a PLA resin and a secondary alkane sulfonate wasadded to the polymer component defining the sheath. The setup of thesystem is the same as described above for Comparative Examples 1, 2, and3.

The fabric was bicomponent 30/70 NatureWorks Grade 6752/NatureWorksGrade 6202/sheath/core made with ionization bars as discussed above tominimize static. At the sheath extruder, 2% by weight of a masterbatchof Sukano Antistatic Product S 546 was combined with NatureWorks Grade6752 to provide the sheath of the fabric. The fabric was produced atspin beam temperatures of 235° C. at the extruder and 240° C. at thedie. The fabric was produced at a fiber draw speed of 3400 m/min and aline speed of 90 m/min. The calender for Inventive Example 3 hadcalender temperatures of 160° C. for the pattern roll and 147° C. forthe anvil roll and a calender pressure of 40 N/mm. Properties ofInventive Example 3 are summarized in Tables 4 and 5 below.

Inventive Example 4

In Inventive Example 4, a 100% PLA bicomponent fabric having asheath/core arrangement was prepared in which 2 weight percent of amasterbatch comprising a PLA resin and a secondary alkane sulfonate wasadded to the polymer component defining the sheath. The setup of thesystem is the same as described above for Comparative Examples 1, 2, and3.

The fabric was a bicomponent 30/70 NatureWorks Grade 6752/NatureWorksGrade 6202/sheath/core made with ionization bars as discussed above tominimize static. At the sheath extruder, 2% by weight of a masterbatchof Sukano Antistatic Product S 546 was combined with NatureWorks Grade6752 to provide the sheath of bicomponent fabric. The fabric ofInventive Example 4 was produced at spin beam temperatures of 235° C. atthe extruder and 240° C. at the die. The fabric of Inventive Example 4was produced at a fiber draw speed of approximately 3400 m/min and aline speed of 241 m/min to yield a calculated basis weight of 15grams/square meter. The calender for Inventive Example 4 had calendertemperatures of 160° C. for the pattern roll and 147° C. for the anvilroll and a calender pressure of 40 N/mm. The mechanical properties ofInventive Example 14 were not evaluated.

TABLE 4 Nonwoven Mechanical Properties MD CD Tensile Tensile per perBasis Basis MD CD Basis MD Weight CD Weight MD% CD% Toughness ToughnessExample Titer Weight Tensile N-m²/ Tensile N-m²/ Elong. Elong. IndexIndex Units DTEX g/m2 N/5cm g-5cm N/5cm g-5cm % % N-% N-% Comparative1.8 23.8 35.1 1.47 13.0 0.546 13.3 24.03 467 312 Example 1 Comparative1.7 39.8 70.7 1.78 26.6 0.668 14.7 28.61 1881 761 Example 2 Comparative2.0 24.3 38.4 1.58 14.8 0.609 15.6 26.30 599 389 Example 3 Inventive 1.727.6 83.2 3.01 29.0 1.051 28.3 44.28 2355 1284 Example 1 Inventive 1.827.6 85.2 3.09 29.0 1.051 29.4 49.44 2505 1434 Example 2 Inventive 1.951.3 142.2 2.77 73.8 1.435 40.8 46.54 5802 3435 Example 3 Inventive —15.0* — — — — — — — — Example 4 *Calculated basis weight for sampleproduced.

TABLE 5 Properties Normalized for Basis Weights. Fabric Root mean SquareMD CD MD CD MD Relative CD Relative Toughness Tensile Tensile ToughnessToughness Toughness Toughness index per Basis per Basis per Basis IndexIndex Index per Index per Basis Weight Weight Weight (MDTI) (CDTI) BasisWeight Basis Weight Weight* Units N-m²/g- N-m²/g- Example g/m² 5 cm 5 cmN-% N-% N-%/g/m² N-%/g/m² N-%/g/m² Comparative 23.8 1.47 0.546  467  31219.62 13.11 16.69 Example 1 Comparative 39.8 1.78 0.668 1881  761 47.2619.12 36.05 Example 2 Comparative 24.3 1.58 0.609  599  389 24.65 16.0120.78 Example 3 Inventive 27.6 3.01 1.051 2355 1284 85.32 46.52 68.12Example 1 Inventive 27.6 3.09 1.051 2505 1434 90.76 51.96 73.95 Example2 Inventive 51.3 2.77 1.435 5802 3435 113.1 66.96 92.94 Example 3${{\text{*}{Root}\mspace{14mu}{Mean}\mspace{14mu}{Square}} = \sqrt{\frac{({MDTI})^{2} + ({CDTI})^{2}}{2}}};$${{Fabric}\mspace{14mu}{Root}\mspace{14mu}{mean}\mspace{14mu}{Square}\mspace{14mu}{Toughness}\mspace{14mu}{Index}\mspace{14mu}{Per}\mspace{14mu}{Basis}\mspace{14mu}{Weight}} = {{\left( \sqrt{\frac{({MDTI})^{2} + ({CDTI})^{2}}{2}} \right)/{Basis}}\mspace{14mu}{weight}}$

TABLE 6 Percent Increase in MD and CD Relative Index in ToughnessInventive Inventive Inventive Example Example Example InventiveInventive Inventive 1 2 3 Example 1 Example 2 Example 3 Example (MD)(MD) (MD) (CD) (CD) (CD) Units (%) (%) (%) (%) (%) (%) ComparativeExample 1 334.9 362.6 476.5 254.8 296.3 410.7 Comparative Example 2 80.592.0 139.3 143.3 171.6 250.2 Comparative Example 3 246.1 268.2 358.8190.6 224.5 318.2 Percent Increase: (ending value- startingvalue)/starting value × 100

TABLE 7 Shrinkage Resistance for PLA Spunbond Fabric Shrink Shrink AreaExample (MD) % (CD)% Shrink % Comparative 3.1 −1.1 2.1 Example 1Comparative 3.1 −1.4 1.8 Example 2 Comparative 2.9 −1.5 1.4 Example 3Inventive 7.8 −0.9 7.0 Example 1 Inventive 6.4 −2.5 4.0 Example 2Inventive 2.2 −3.3 −1.0 Example 3

From Tables 4 and 5 above, it can be seen that the inventive nonwovenfabrics exhibit significant improvements in mechanical properties incomparison to the identically prepared nonwoven fabrics that do notinclude the secondary alkane sulfonate. In this regard, the resultsprovided in Table 5 are particularly telling. In Table 5, the resultshave been normalized to account for the differences in basis weights.Based on this data, it can be seen that the inventive nonwoven fabricsexhibited an increase in tensile strengths of greater than 50% incomparison to the comparative examples. For example, the inventivenonwoven fabrics exhibited an increase in MD tensile strength rangingfrom 55.6% (comparison of Inventive Example 3 and Comparative Example 2)to 110.2% (comparison of Inventive Example 2 and Comparative Example 1).For CD tensile strength, the inventive nonwoven fabrics exhibited anincrease in CD tensile strength ranging from 57.3% (comparison ofInventive Example 1 and Comparative Example 2) to 162.8% (comparison ofInventive Example 3 and Comparative Example 1).

The inventive nonwoven fabrics also exhibited significant increases intoughness in comparison to the nonwoven fabrics of the comparativeexamples. Table 5 below shows both MD and CD Relative Index of Toughness(normalized for basis weight) for Comparative Examples 1-3 and InventionExamples 1-3. For example, the inventive nonwoven fabrics exhibited anincrease in MD Relative Index of Toughness ranging from 80.5%(comparison of Inventive Example 1 and Comparative Example 2) to 476%(comparison of Inventive Example 3 and Comparative Example 1). For theCD Relative Index of Toughness, the inventive nonwoven fabrics exhibitedan increase in CD Relative Index of Toughness ranging from 143%(comparison of Inventive Example 1 and Comparative Example 2) to 411%(comparison of Inventive Example 3 and Comparative Example 1).

When comparing properties of different nonwovens it is often useful tocompare the root mean square of the combined values of the MD and CDproperty of interest. This method allows comparison of single values.The root mean square provides a single number that combines input fromboth the MD and the CD values by taking the square root of the sum ofthe square of the MD value plus the square of the CD value. Use of theroot mean square method to combine the MD and the CD results isparticularly useful if samples to be compared were made on differentmachines or under some different condition that might influence theMD/CD ratio. Table 5 below shows the root mean square of the ToughnessIndex per basis weight for the Comparative Samples 1-3 as well as theInvention samples 1-3. The Root Mean Square Toughness Index valuesnormalized for basis weight show the comparative samples grouped between10 and 40 N-%/g/m². In contrast, the inventive nonwoven fabricsexhibited Root Mean Square Toughness Index values above 65 N-%/g/m², andin particular, within a range of 55 to 100 N-%/g/m². Thus, a very clearseparation in the root mean square of the normalized Index of Toughnessvalues can be seen for fabrics of the invention and the comparativesamples.

To further evaluate the basis for the increases in tensile strengths,elongation, and toughness of the inventive nonwoven fabrics, SEM imagesof the fabric surfaces of Comparative Example 1 and Inventive Example 1were obtained. FIGS. 1A and 1B are SEM images of Comparative Example 1taken at a magnification of 250× and 100×, respectively. FIGS. 2A and 2Bare SEM images of Inventive Example 1 taken at a magnification of 250×and 100×, respectively. The images were obtained with a PERSONAL SEM 75,available from RJ Lee Instruments Ltd., and a DESK V Sputterer,available from Denton Vacuum. As the SEM images were made at lowmagnification, 100× and 250×, sputtering with gold was not required. 5mm×5 mm samples of each fabric were obtained and placed with in the SEMinstrument. A low vacuum was obtained, and then the images werecaptured.

Surprisingly, a significant difference in bonding between the fibers wasobserved. In particular, the bond points of the fabric of ComparativeExample 1 showed that the individual fibers were loosely bondedtogether, and that there was minimal polymer flow bonding adjacentfibers to each other. In comparison, the bond points of the fabric ofInventive Example 1, showed significant melting and flowing of thepolymer of the individual fibers. Thus, the inventive fabric exhibitedsignificant improvements in bonding in comparison to the comparativefabric that did not include the secondary alkane sulfonate.

In the following examples, the effect of the carrier resin for thesecondary alkane sulfonate on the physical properties was explored. Asexplained below, the improvements in mechanical properties in thefabrics were shown to be due primarily to the presence of the secondaryalkane sulfonate, and not to the presence of a lower molecular weightcarrier resin in the masterbatch.

Comparative Example 4

In Comparative Example 4, a 100% PLA bicomponent fabric having asheath/core arrangement was prepared in which 0.5% weight percent ofNatureWorks Grade 6302 was added to the polymer component defining thesheath. NatureWorks Grade 6302 is commonly used as the carrier polymerfor masterbatches added to PLA polymer formulations. It is thereforebelieved that this PLA resin provides a good approximation of the PLAresin in the secondary alkane sulfonate. The setup of the system is thesame as described above for Comparative Examples 1, 2, and 3.

The fabric was a bicomponent 30/70 NatureWorks Grade 6752/NatureWorksGrade 6202/sheath/core made with ionization bars as discussed above tominimize static. At the sheath extruder, 0.5% weight percent ofNatureWorks Grade 6302 2% by weight was combined with NatureWorks Grade6752 to provide the sheath of bicomponent fabric. The fabric ofComparative Example 4 was made at processing conditions similar to thoseused for Inventive Examples 1-4, with the exceptions as shown in Table 8below and the line speed was adjusted to provide a final basis weight of25 GSM. Properties of Comparative Example 4 are summarized below inTable 9, below.

Comparative Example 5

In Comparative Example 5 a 100% PLA bicomponent fabric having asheath/core arrangement was prepared in which 1.0% weight percent ofNatureWorks Grade 6302 was added to the polymer component defining thesheath. The setup of the system is the same as described above forComparative Examples 1, 2, and 3.

The fabric was a bicomponent 30/70 NatureWorks Grade 6752/NatureWorksGrade 6202/sheath/core made with ionization bars as discussed above tominimize static. At the sheath extruder, 1.0% weight percent ofNatureWorks Grade 6302 2% by weight was combined with NatureWorks Grade6752 to provide the sheath of bicomponent fabric. The fabric ofComparative Sample 4 was made at processing conditions similar to thoseused for Inventive Examples 1˜4 except as shown in Table 8, below, andthe line speed was adjusted to provide a final basis weight of 25 GSM.Properties of Comparative Example 5 are summarized below in Table 9.

Comparative Example 6

In Comparative Example 6 a 100% PLA bicomponent fabric having asheath/core arrangement was prepared in which 2.0% weight percent ofNatureWorks Grade 6302 was added to the polymer component defining thesheath. The setup of the system is the same as described above forComparative Examples 1, 2, and 3.

The fabric was a bicomponent 30/70 NatureWorks Grade 6752/NatureWorksGrade 6202/sheath/core made with ionization bars as discussed above tominimize static. At the sheath extruder, 2.0% weight percent ofNatureWorks Grade 6302 2% by weight was combined with NatureWorks Grade6752 to provide the sheath of bicomponent fabric. The fabric ofComparative Example 6 was made at processing conditions similar to thoseused for Inventive Examples 1˜4 except as shown in Table 8, below, andthe line speed was adjusted to provide a final basis weight of 25 GSM.Properties of Comparative Example 6 are summarized below in 9, below.

Comparative Example 7

In Comparative Example 7 a 100% PLA bicomponent fabric having asheath/core arrangement was prepared in which 3.5% weight percent ofNatureWorks Grade 6302 was added to the polymer component defining thesheath. The setup of the system is the same as described above forComparative Examples 1, 2, and 3.

The fabric was a bicomponent 30/70 NatureWorks Grade 6752/NatureWorksGrade 6202/sheath/core made with ionization bars as discussed above tominimize static. At the sheath extruder, 3.5% weight percent ofNatureWorks Grade 6302 2% by weight was combined with NatureWorks Grade6752 to provide the sheath of bicomponent fabric. The fabric ofComparative Sample 7 was made at processing conditions similar to thoseused for Examples of this invention 1-4 except as shown in Table 8,below, and the line speed was adjusted to provide a final basis weightof 25 GSM. Properties of Comparative Sample 7 are summarized below inTable 9, below.

Inventive Example 5

In Inventive Example 5, a 100% PLA bicomponent fabric having asheath/core arrangement was prepared in which 0.3 weight percent of amasterbatch comprising a PLA resin and a secondary alkane sulfonate wasadded to the polymer component defining the sheath. The setup of thesystem is the same as described above for Comparative Examples 1, 2, and3.

The fabric was a bicomponent 50/50 NatureWorks Grade 6752/NatureWorksGrade 6202/sheath/core made with ionization bars as discussed above tominimize static. At the sheath extruder, 0.3% by weight of a masterbatchof Sukano Product S 546 was combined with NatureWorks Grade 6752 toprovide the sheath of bicomponent fabric. The fabric of InventiveExample 5 was produced was made at processing conditions similar tothose used for Inventive Examples 1-4 except as shown in Table 8, below,and the line speed was adjusted to provide a final basis weight of 28GSM. Properties of Inventive Example 5 are summarized below in Table 9,below.

Inventive Example 6

In Inventive Example 5, a 100% PLA bicomponent fabric having asheath/core arrangement was prepared in which 0.3 weight percent of amasterbatch comprising a PLA resin and a secondary alkane sulfonate wasadded to the polymer component defining the sheath. The setup of thesystem is the same as described above for Inventive Examples 1, 2, and3.

The fabric was a bicomponent 50/50 NatureWorks Grade 6752/NatureWorksGrade 6202/sheath/core made with ionization bars as discussed above tominimize static. At the sheath extruder, 0.3% by weight of a masterbatchof Sukano Product S 546 was combined with NatureWorks Grade 6752 toprovide the sheath of bicomponent fabric. The fabric of InventiveExample 6 was produced was made at processing conditions similar tothose used for Inventive Examples 1-4 except as shown in Table 8 below,and the line speed was adjusted to provide a final basis weight of 23GSM. Properties of Inventive Example 6 are summarized below in Table 9,below.

TABLE 8 Process Conditions for Comparative Examples 4-7 and InventiveExamples 5-6 Calender Temperature Cabin (Embossed/ Calender Through-PutPressure Smooth) Pressure Gap Units Example Kg/hr Pa C./C. N/mm SettingComparative 230 6000 165/140 40 22/26 Example 4 Comparative 230 6000165/140 40 22/26 Example 5 Comparative 230 6000 165/140 40 22/26 Example6 Comparative 230 6000 165/140 40 22/26 Example 7 Inventive 240 6500152/142 40 20/24 Example 5 Inventive 240 6500 152/142 40 20/24 Example 6

TABLE 9 Mechanical Properties MD CD MD CD Tensile Tensile MD CDToughness Toughness Basis per Basis CD per Basis MD% CD% ToughnessToughness Index per Index per Example Titer Weight Tensile WeightTensile Weight Elong. Elong. Index Index BW BW Units DTEX g/m² N/5cmN-m²/g-5cm N/5cm N-m²/g-5cm % % N-% N-% N-%/gsm N-%/gsm Comparative 1.823.12 38.97 1.69 13.85 0.599 14.75 25.33 574.81 477.47 24.86 20.65Example 4 Comparative No 28.37 35.33 1.24 12.59 0.444 13.17 24.39 465.30307.07 16.40 10.82 Example 5 Data Comparative No 22.62 34.87 1.54 12.160.537 13.21 24.56 460.63 298.40 20.36 13.19 Example 6 Data ComparativeNo 23.38 34.24 1.46 12.94 0.553 12.58 26.79 430.74 346.67 18.42 14.83Example 7 Data Inventive 2.40 28.37 69.48 2.45 20.96 0.739 23.64 32.321642.51 677.43 57.90 23.88 Example 5 Inventive 2.07 23.12 52.93 2.8915.43 0.667 25.18 32.79 1332.78 505.95 57.65 21.88 Example 6

There was no visible difference in the bonding sites for nonwovensfabrics above (Comparative Examples 4-7) made with PLA 6302 used as anadditive versus nonwovens above made using addition of the masterbatchof Sukano Product 546 (Inventivw Examples 5 and 6). However, as from themechanical data summarized in Table 9, a significant difference betweenthe Comparative Examples and Inventive Examples 5 and 6 was observed. Inparticular, the examples including secondary alkane sulfonate exhibitedsignificant improvements in MD and CD tensile strength, MD and CDelongation, and MD and CD Toughness Index in comparison to thecomparative examples that only include the masterbatch PLA resin, but nosecondary alkane sulfonate. Accordingly, it can be seen that theimprovement in properties are attributed to the presence of thesecondary alkane sulfonate, and not to the lower molecular weight PLAresin of the masterbatch.

It was also observed that during the manufacture of the fabrics, thefabrics of Inventive Examples 5 and 6 were more stable during calenderbonding calender in comparison to the fabrics of Comparative Examples4-7.

In the following examples, the hydrophilic nature of the PLA fabrics,and the effects of the secondary alkane sulfonate on the hydrophilicityof the fabrics were investigated. Inventive Examples 7-12 were preparedin accordance with the fabric of Inventive Fabrics 6 and 7. In eachexample, the amount of Sukano additive added to the sheath was variedand the effects on liquid Run-Off and Strike-through was evaluated atdifferent time periods. The results are summarized in Tables 10 and 11,below.

Run-Off data was measured in accordance with the procedures set forth inWSP 80.9, and Strikethrough data as measured by test method WSP 70.3.

Runoff data measures the percent of a specified volume of fluid thatruns off a fabric/absorbent combination that is supported at a specifiedangle from vertical. The fabric being evaluated is positioned overlyingan absorbent material. During the test procedure, a fluid runs down thefabric and may, or may not, be absorbed into the absorbent materialplaced under the fabric being tested. If the fabric is hydrophobic avery high % of the fluid runs down and off the fabric/absorbentcombination into a container for collection. If the fabric is veryhydrophilic nearly all of the liquid is absorbed by the fabric/absorbentcombination and the % Run-off is nearly equal to zero. The Runoff testis commonly repeated on the same piece of fabric three times. Thisprocedure simulates multiple voids by the baby or adult into the diaper.Most typical commercial topsheets show a very low % run-off in the firstinsult. However the Run-off values commonly increases in the second andthird insults as the surfactant is washed off and transported into theabsorbent material under the test fabric. Thus, all hydrophilicsurfactant may be lost following a first voiding. As a result, repeatedvoidings by a wearer, such as a baby, may result in loss ofhydrophilicity of the fabric, which may undesirably lead to leakage ofthe diaper.

Strike Through data measures the time for a specified volume of liquidapplied at downward at a 90 degree angle to the a test fabric surfacethat is backed by an absorbent layer. The strike though values after oneor multiple insults can be measured. A low strike through value suggeststhat liquid will rapidly penetrate the hydrophilic treated fabric and beabsorbed by the absorbent material simulated the core of the diaper.Results after multiple strike through tests provide an indication of thepermanence of the surfactant treatment. Increasing values ofstrikethrough with multiple insults suggests that the surfactant isbeing washed into the underlying absorbent material, such as anabsorbent core, with risk that the diaper topsheet will becomehydrophobic and the diaper will leak. An optimized topsheet will providestrikethrough values of 4 seconds or less even after up to threeinsults.

TABLE 10 Run-Off Test Results % Run-Off % Run-Off % Run Off % Run Off %Run Off % Run Tested Tested 24 Tested 14 Tested 14 Tested 14 Off 30 %Run Off 30 % Run Off Sukano Fresh as Hours after days after days afterdays after days after days after 30 days after Additive Made Made MadeFirst Made Second Made Third Made Made Made Third Example Level % FirstGush First Gush Gush Gush Gush First Gush Second Gush Gush Example 0.25%98.6 99.5 96.36 96.16 96.92 98.85 92.20 86.48 7 Example 0.5% 98.3 98.895.88 96.08 95.36 98.97 98.20 98.99 8 Example 1.0% 98.4 97.6 — — — 98.016.87 2.15 9 Example .,5% 98.4 98.3 — — — 97.15 0.00 0.11 10 Example 2%98.0 97.7 — — — 95.79 0.00 0.00 11 Example 2.5% 93.0 89.4 — — — 72.910.00 0.00 12

TABLE 11 Strike-through Test Results Strike - Strike Strike - Strike -Strike - Through Through Through Through Through Strike - Strike -Strike - (Sec.) (Sec.) (Sec.) (Sec.) (Sec.) Through Through ThroughTested Tested 24 Tested 14 Tested 14 Tested 14 (Sec.) (Sec.) (Sec.) 30days Sukano Fresh as Hours after days after days after days after 30days 30 days after 30 days after Additive Made Made Made First Made MadeThird after Made Made after Made Example Level % First Gush First GushGush Second Gush Gush First Gush Second Gush Third Gush Example 7 0.25%8.2 9.3 4.95 4.86 4.43 8.34 5.43 5.03 Example 8 0.5% 8.6 8.4 6.09 4.423.58 4.65 3.70 3.28 Example 9 1.0% 9.6 8.6 — — — 5.15 1.95 2.30 Example10 1.5% 5.9 5.5 — — — 4.08 1.90 2.38 Example 11 2% 4.4 4.3 — — — 3.351.90 2.16 Example 12 2.5% 2.9 3.4 — — — 1.88 2.00 2.18

The % Run-Off and Strike-Through Data in Tables 10 and 11 surprisinglydemonstrated that not only does the secondary alkane sulfonate improvethe mechanical properties of the PLA fabric, but it also modifies theliquid transport properties of the fabrics.

In addition, the results demonstrate that the Run-Off and Strike-throughare dependent, at least in part, on the level of the secondary alkanesulfonate as well as age of the fabric. For example, at two weeks 100%PLA fabric containing 0.25% and 0.5% of the additive exhibitedhydrophobic properties as measured by both runoff and strikethrough.After a month following production, the fabrics containing 0.25% and0.5% of the additive still exhibited hydrophobic properties. However, athigher additive levels a response is observed suggestive of decreasinghydrophobicity. Surprising and unexpected, the response is opposite tothat seen with typical surfactant treated topsheet. Initial runoff andstrikethrough suggests a hydrophobic fabric. However, following thesecond and third insults, the fabric exhibits hydrophilic properties.

This effect suggests that fabrics in accordance with the invention maybe prepared that provide hydrophilic properties following multiplevoids. In particular, fabrics for use as a topsheet may be prepared inwhich the fabric is treated with a low add-on surfactant to provideinitial hydrophilicity, but then takes advantage of the additive toprovide a wash-off resistant hydrophilicity after multiple insults. Sucha topsheet may be of particular interest for use in overnight diapersand incontinent products.

Non-Limiting Exemplary Embodiments

Having described various aspects and embodiments of the inventionherein, further specific embodiments of the invention include those setforth in the following paragraphs.

Certain embodiments according to the invention are directed to aspunbond nonwoven fabric comprising a plurality of fibers that arebonded to each other to form a coherent web, wherein the fibers comprisea blend of a polylactic acid (PLA) and at least one secondary alkanesulfonate. In some embodiments, the blend is present at a surface of theplurality of fibers. In one embodiment, the at least one secondaryalkane sulfonate comprises an alkane chain having from C₁₀-C₁₈, andwherein at least one of the secondary carbons of the alkane chainincludes a sulfonate moiety. For example, the at least one secondaryalkane sulfonate has one of the following structures:

wherein m+n is a number between 7 and 16, and X is independently a C₁-C₄alkyl or absent. In some embodiments, the at least one secondary alkanesulfonate has the following structure:

wherein m+n is a number between 8 and 15, and in particular, wherein m+nis a number between 11 and 14. In some embodiments, the at least onesecondary alkane sulfonate comprises a salt of sodium or potassium.

In certain embodiments, the at least one secondary alkane sulfonate ispresent in an amount ranging from about 0.0125 to 2.5 weight percent,based on the total weight of the fiber. For example, the fiber may havea sheath/core bicomponent arrangement in which the blend is present inthe sheath, and wherein the secondary alkane sulfonate is present in thesheath in an amount ranging from about 0.1 to 0.75 weight percent, basedon the total weight of the sheath. In another embodiment, the fiber mayhave a sheath/core bicomponent arrangement in which the blend is presentin the sheath, and wherein the secondary alkane sulfonate is present inthe sheath in an amount ranging from about 0.2 to 0.6 weight percent,based on the total weight of the sheath. In yet another embodiment, thefiber has a sheath/core bicomponent arrangement in which the blend ispresent in the sheath, and wherein the secondary alkane sulfonate ispresent in the sheath in an amount ranging from about 0.3 to 0.4 weightpercent, based on the total weight of the sheath.

In one embodiment, the plurality of fibers comprise bicomponent fibers.In some embodiments, the plurality of fibers comprise bicomponent fibersand the at least one secondary alkane sulfonate is present in only oneof the component of the fibers. In one embodiment, the bicomponentfibers have a sheath/core configuration and the sheath comprises a blendof the PLA and the at least one secondary alkane sulfonate. In someembodiments, the core comprises PLA and does not include the at leastone secondary alkane sulfonate. In still other embodiments, thebicomponent fibers comprise a side-by-side arrangement.

In one embodiment, the core comprises at least one of a polyolefin, apolyester, a PLA, or any combination thereof. In a preferred embodiment,each of the sheath and the core comprises PLA. In certain embodiments,the sheath comprises a first PLA grade, the core comprises a second PLAgrade, and the first PLA grade and the second PLA grade are different.

In some embodiments, the fabric exhibits an increase in tensile strengthin at least one of the machine direction or cross direction incomparison to an identical fabric that does not include the at least onesecondary alkane sulfonate. For example, the fabric may exhibit anincrease in tensile strength in at least one of the machine direction orcross direction of at least 50% in comparison to an identical fabricthat does not include the at least one secondary alkane sulfonate.

In one embodiment, the fabric exhibits an increase in tensile strengthin at least one of the machine direction or cross direction that is from50% to 200% in comparison to an identical fabric that does not includethe at least one secondary alkane sulfonate.

In one embodiment, the fabric exhibits an increase in machine directiontensile strength that is from about 50 to 150% in comparison to anidentical fabric that does not include the at least one secondary alkanesulfonate.

In one embodiment, the fabric exhibits an increase in machine directiontensile strength that is from about 55 to 125% in comparison to anidentical fabric that does not include the at least one secondary alkanesulfonate.

In one embodiment, the fabric exhibits an increase in machine directiontensile strength that is from about 65 to 110% in comparison to anidentical fabric that does not include the at least one secondary alkanesulfonate.

In one embodiment, the fabric exhibits an increase in machine directiontensile strength that is from about 65 to 110% in comparison to anidentical fabric that does not include the at least one secondary alkanesulfonate.

In one embodiment, the fabric exhibits an increase in machine directiontensile strength that is from about 85 to 110% in comparison to anidentical fabric that does not include the at least one secondary alkanesulfonate.

In one embodiment, the fabric exhibits an increase in machine directiontensile strength that is from about 90 to 110% in comparison to anidentical fabric that does not include the at least one secondary alkanesulfonate.

In one embodiment, the fabric exhibits an increase in cross directiontensile strength that is from about 50 to 200% in comparison to anidentical fabric that does not include the at least one secondary alkanesulfonate.

In one embodiment, the fabric exhibits an increase in cross directiontensile strength that is from about 50 to 170% in comparison to anidentical fabric that does not include the at least one secondary alkanesulfonate.

In one embodiment, the fabric exhibits an increase in cross directiontensile strength that is from about 55 to 165% in comparison to anidentical fabric that does not include the at least one secondary alkanesulfonate.

In one embodiment, the fabric exhibits an increase in cross directiontensile strength that is from about 65 to 160% in comparison to anidentical fabric that does not include the at least one secondary alkanesulfonate.

In one embodiment, the fabric exhibits an increase in cross directiontensile strength that is from about 85 to 150% in comparison to anidentical fabric that does not include the at least one secondary alkanesulfonate.

In one embodiment, the fabric exhibits an increase in cross directiontensile strength that is from about 90 to 125% in comparison to anidentical fabric that does not include the at least one secondary alkanesulfonate.

In one embodiment, the fabric exhibits an increase in elongation in atleast one of the machine direction or cross direction in comparison toan identical fabric that does not include the at least one secondaryalkane sulfonate.

In one embodiment, the fabric exhibits a machine direction Index ofToughness that is from about 2,000 to 7,500 N-%.

In one embodiment, the fabric exhibits a machine direction Index ofToughness that is from about 2,300 to 6,500 N-%.

In one embodiment, the fabric exhibits a machine direction Index ofToughness that is from about 2,300 to 6,000 N-%.

In one embodiment, the fabric exhibits a cross direction Index ofToughness that is from about 1,000 to 5,000 N-%.

In one embodiment, the fabric exhibits a cross direction Index ofToughness that is from about 1,250 to 5,000 N-%.

In one embodiment, the fabric exhibits a cross direction Index ofToughness that is from about 1,250 to 3,500 N-%.

In one embodiment, the fabric exhibits an increase in machine directionIndex of Toughness that is from about 20 to 1,250% in comparison to anidentical fabric that does not include the at least one secondary alkanesulfonate.

In one embodiment, the fabric exhibits an increase in machine directionIndex of Toughness that is at least 100% in comparison to an identicalfabric that does not include the at least one secondary alkanesulfonate.

In one embodiment, the fabric exhibits an increase in cross directionIndex of Toughness that is from about 50 to 1,000% in comparison to anidentical fabric that does not include the at least one secondary alkanesulfonate.

In one embodiment, the fabric exhibits an increase in cross directionIndex of Toughness that is at least 85% in comparison to an identicalfabric that does not include the at least one secondary alkanesulfonate.

In some embodiments, the fabric exhibits a machine direction RelativeIndex of Toughness that is from about 50 to 150 N-%/g/m², such as amachine direction Relative Index of Toughness that is from about 75 to125 N-%/g/m², and in particular, a machine direction Relative Index ofToughness that is from about 85 to 115 N-%/g/m². In one embodiment, thefabric exhibits a cross direction Relative Index of Toughness that isfrom about 40 to 100 N-%/g/m², such as a cross direction Relative Indexof Toughness that is from about 45 to 85 N-%/g/m².

In certain embodiments, the fabric exhibits an increase in machinedirection Relative Index of Toughness that is from about 100 to 1,000%in comparison to an identical fabric that does not include the at leastone secondary alkane sulfonate, such as an increase in machine directionRelative Index of Toughness that is from 80 to 500% in comparison to anidentical fabric that does not include the at least one secondary alkanesulfonate.

In one embodiment, the fabric exhibits an increase in cross directionRelative Index of Toughness that is at least 100% in comparison to anidentical fabric that does not include the at least one secondary alkanesulfonate, such as an increase in cross direction Relative Index ofToughness that is from about 140 to 410% in comparison to an identicalfabric that does not include the at least one secondary alkanesulfonate.

Additional aspects of the invention are directed to a spunbond nonwovenfabric comprising a plurality of fibers that are bonded to each other toform a coherent web, wherein the fibers comprise from 95 to 100%polylactic acid (PLA), and wherein the fibers exhibit a root mean squareof a Toughness Index per basis weight having a value that is at least 55N-%/g/m². In one such embodiment, the root mean square of the ToughnessIndex per basis weight is a value that is greater than 65 N-%/g/m², suchas a value from about from about 65 to 150 N-%/g/m². In one embodiment,the fibers of the fabric comprise less than 5 weight % of additives.

Aspects of the invention are also directed to absorbent articlescomprising a nonwoven fabric having fibers comprising a blend of a PLAresin and at least one secondary alkane sulfonate. Examples of absorbentarticles include diapers and femine sanitary pads.

Additional aspects of the invention are directed to a process forpreparing a polylactic acid (PLA) spunbond nonwoven fabric, the processcomprising: blending a PLA resin and at least one secondary alkanesulfonate, under heat and pressure, to form a stream of molten orsemi-molten PLA resin; forming a plurality of PLA continuous filamentsfrom said stream; depositing the plurality of PLA continuous filamentsonto a collection surface; exposing the plurality of PLA continuousfilaments to ions; and bonding the plurality of PLA continuous filamentsto form the PLA spunbond nonwoven fabric, wherein the continuousfilaments comprise a blend of PLA and the at least one secondary alkanesulfonate.

In one embodiment, the filaments comprise a blend of PLA and the atleast on secondary alkane sulfonate. The filaments may be monocomponentor bicomponent. In a preferred embodiment, the filaments have asheath/core bicomponent configuration in which the sheath comprises theblend of the PLA and the at least one secondary alkane sulfonate. Insome embodiments, the core may comprise PLA or a synthetic polymer, suchas a polyolefin or a polyester. Preferably, the core comprises PLA.

Advantageously, the process may be performed at relatively high drawspeeds. For example, the continuous filaments may be drawn at a fiberdraw speed greater than about 2500 m/min., such as a fiber draw speedfrom about 3000 m/min to about 5500 m/min., or a fiber draw speed fromabout 3000 m/min to about 4000 m/min.

In one embodiment, the step of exposing the plurality of PLA continuousfilaments to ions comprising passing the filaments in close proximity toan ionization source, such as an ionization bar. In one embodiment, theionization source comprises an ionization bar that is positioned abovethe collection surface, and in the cross direction of the fabric.

In one embodiment, the step of bonding the continuous filaments to formthe PLA spunbond nonwoven fabric comprises thermal point bonding the webwith heat and pressure via a calender having a pair of cooperating rollsincluding a patterned roll. In some embodiments, the thermal pointbonding the continuous filaments comprises imparting a three-dimensionalgeometric bonding pattern onto the PLA spunbond nonwoven fabric.

In one embodiment, the bonding of the pattern onto the PLA spunbondnonwoven fabric comprises imparting at least one of a diamond pattern, ahexagonal dot pattern, an oval-elliptic pattern, a rod-shaped pattern,or any combination thereof onto the PLA spunbond nonwoven fabric. Insome embodiments, the bonding pattern covers from about 5% to about 30%of the surface area of the patterned roll. For example, the bondingpattern may cover from about 10% to about 25% of the surface area of thepatterned roll.

In one embodiment, the process additionally comprises dissipating staticcharge from the PLA spunbond nonwoven fabric proximate to the calendervia a first static control unit. In one embodiment, the static controlunit comprises a second ionization source, such as an ionization bar.For instance, the second ionization source may comprise an ionizationbar extending over at least one of the plurality of PLA continuousfilaments or the PLA spunbond nonwoven fabric in a cross direction.

In one embodiment, dissipating static charge from the PLA spunbondnonwoven fabric comprises contacting the PLA spunbond nonwoven fabricwith a static bar.

In some embodiments, the process may further comprise cutting the PLAspunbond nonwoven fabric to form cut PLA spunbond nonwoven fabric;exposing the cut PLA spunbond nonwoven fabric to ions via a thirdionization source; and winding the cut PLA spunbond nonwoven fabric intorolls. In one embodiment, the third ionization source comprises anionization bar extending over at least one of the plurality of PLAcontinuous filaments or the PLA spunbond nonwoven fabric in a crossdirection.

Additional aspects of the invention are directed to a system forpreparing a polylactic acid (PLA) spunbond nonwoven fabric, the systemcomprising: a first PLA source and a source of a secondary alkanesulfonate, configured to provide a stream comprising molten orsemi-molten PLA resin and the secondary alkane sulfonate; a spin beam influid communication with the first PLA source, the spin beam configuredto extrude and draw a plurality of PLA continuous filaments, wherein thePLA continuous filaments comprise a blend of the PLA and the secondaryalkane sulfonate; a collection surface disposed below an outlet of thespin beam onto which the PLA continuous filaments are deposited to formthe PLA spunbond nonwoven fabric; a first ionization source positionedand arranged to expose the PLA continuous filaments to ions; and acalender positioned downstream of the first ionization source.

In one embodiment, the first ionization source is positioned above thecollection surface and downstream of a point at where the PLA continuousfilaments are deposited on the collection surface. In anotherembodiment, the first ionization source is positioned between the outletof the spin beam and the collection surface. Preferably, the firstionization source and the collection surface are separated by a distancefrom about 1 inch to about 24 inches, such as a distance from about 1inch to about 12 inches, and in particular, a distance from about 1 inchto about 5 inches.

In some embodiments, the system may further comprise a static controlunit positioned and arranged to dissipate static from the PLA spunbondnonwoven fabric proximate to the calender. In one embodiment, the staticcontrol unit comprises a passive static bar, or a second ionizationsource, or a combination thereof.

In one embodiment, the system includes a press roll positioneddownstream from the outlet of the spin beam. In some embodiments, thesystem may comprise a vacuum source disposed below the collectionsurface.

In certain embodiments, the system may include a winder positioneddownstream from the calender; and a third ionization source positionedand arranged to expose the PLA spunbond nonwoven fabric to ionsproximate to the winder.

In one embodiment, the at least one of the first ionization source, thestatic control source, and the third ionization source each comprise anionization bar extending over at least one of the plurality of PLAcontinuous filaments or the PLA spunbond nonwoven fabric in a crossdirection. In one embodiment, the first ionization source, the staticcontrol source, and the third ionization source are configured toactively dissipate static charge created during preparation of the PLAspunbond nonwoven fabric.

In one embodiment, the first ionization source is positioned downstreamfrom the press roll. In some embodiments, the first ionization source ispositioned between the spin beam and the press roll. When present, thestatic control unit may be positioned upstream from, and adjacent to,the calender. In other embodiments, the static control unit ispositioned downstream from, and adjacent to, the calender.

In one embodiment, the calender comprises a pair of cooperating rollsincluding a patterned roll, the patterned roll comprising athree-dimensional geometric bonding pattern. In some embodiments, thebonding pattern comprises at least one of a diamond pattern, a hexagonaldot pattern, an oval-elliptic pattern, a rod-shaped pattern, or anycombination thereof. In one embodiment, the bonding pattern covers fromabout 5% to about 30% of the surface area of the patterned roll, such asfrom about 10% to about 25% of the surface area of the patterned roll.

In one embodiment, the system is configured to produce a nonwoven fabricof continuous filaments having a bicomponent arrangement. In oneembodiment, the continuous filaments have a sheath/core arrangement. Ina preferred embodiment, the system is configured to produce filaments inwhich the blend of the PLA and the secondary alkane sulfonate definesthe sheath. In some embodiments, the core comprises a PLA resin. The PLAresin may be the same or different than that of the sheath. In oneembodiment, the core is free of the secondary alkane sulfonate.

In some embodiments, the secondary alkane sulfonate is present in anamount ranging from about 0.0125 to 2.5 weight percent, based on thetotal weight of the fiber. In one embodiment, the continuous filamentshave a sheath/core bicomponent arrangement in which the blend is presentin the sheath, and wherein the secondary alkane sulfonate is present inthe sheath in an amount ranging from about 0.1 to 0.75 weight percent,based on the total weight of the sheath.

In one particular embodiment, the system is configured to preparecontinuous filaments having a sheath/core bicomponent in which the blendis present in the sheath, and wherein the secondary alkane sulfonate ispresent in the sheath in an amount ranging from about 0.2 to 0.6 weightpercent, based on the total weight of the sheath. In other embodiments,the system is configured to produce continuous filaments having asheath/core bicomponent arrangement in which the blend is present in thesheath, and wherein the secondary alkane sulfonate is present in thesheath in an amount ranging from about 0.3 to 0.4 weight percent, basedon the total weight of the sheath.

Modifications of the invention set forth herein will come to mind to oneskilled in the art to which the invention pertains having the benefit ofthe teachings presented in the foregoing descriptions and the associateddrawings. Therefore, it is to be understood that the invention is not tobe limited to the specific embodiments disclosed and that modificationsand other embodiments are intended to be included within the scope ofthe appended claims. Although specific terms are employed herein, theyare used in a generic and descriptive sense only and not for purposes oflimitation.

That which is claimed:
 1. A nonwoven fabric comprising a plurality offibers that are bonded to each other to form a coherent web, wherein thefibers comprise a hydrophobic polymeric blend of a biobased aliphaticpolyester and at least one secondary alkane sulfonate.
 2. The nonwovenfabric of claim 1, wherein the fabric exhibits at least one of thefollowing: an increase in tensile strength in at least one of themachine or cross direction in comparison to an identical fabric thatdoes not include the at least one secondary alkane sulfonate; and anincrease in elongation in at least one of the machine direction or crossdirection in comparison to an identical fabric that does not include theat least one secondary alkane sulfonate.
 3. The fabric of claim 1,wherein the biobased aliphatic polyester comprises polylactic acid (PLA)or polybutylene succinate.
 4. The fabric of claim 1, wherein the blendis present at a surface of the plurality of fibers.
 5. The fabric ofclaim 1, wherein the at least one secondary alkane sulfonate comprisesan alkane chain having from C₁₀-C₁₈, and wherein at least one of thesecondary carbons of the alkane chain includes a sulfonate moiety. 6.The fabric of claim 1, wherein the at least one secondary alkanesulfonate has one of the following structures:

wherein m+n is a number between 7 and 16, and X is independently a C₁-C₄alkyl or absent.
 7. The fabric of claim 1, wherein the at least onesecondary_alkane sulfonate comprises a salt of sodium or potassium. 8.The fabric of claim 1, wherein the at least one secondary alkanesulfonate is present in an amount ranging from about 0.0037525 to 1weight percent, based on the total weight of the fiber.
 9. The fabric ofclaim 1, wherein the fiber has a sheath/core bicomponent arrangement inwhich the blend is present in the sheath, and wherein the secondaryalkane sulfonate is present in the sheath in an amount ranging fromabout 0.0125 to 0.5 weight percent, based on the total weight of thesheath.
 10. The fabric of claim 1, wherein plurality of fibers comprisebicomponent fibers.
 11. The fabric of claim 10, wherein the bicomponentfibers have a sheath/core configuration and each of the sheath and thecore comprises PLA.
 12. The fabric of claim 1, wherein plurality offibers comprise bicomponent fibers and the at least one secondary alkanesulfonate is present in only one of the component of the fibers.
 13. Thefabric of claim 12, wherein the bicomponent fibers have a sheath/coreconfiguration and the sheath comprises said blend of the PLA and the atleast one secondary alkane sulfonate.
 14. The fabric of claim 1, whereinthe fabric exhibits a machine direction Index of Toughness that is fromabout 2,000 to 7,500 N-%.
 15. The fabric of claim 1, wherein theplurality of fibers are bonded via calender bonding or air throughbonding.
 16. An absorbent article comprising the fabric of claim
 1. 17.The absorbent article of claim 15, wherein the article comprises adiaper or a sanitary pad.
 18. A process for preparing a polylactic acid(PLA) spunbond nonwoven fabric, the process comprising: blending a PLAresin and at least one secondary alkane sulfonate, under heat andpressure, to form a stream of molten or semi-molten PLA resin; forming aplurality of PLA continuous filaments from said stream; depositing theplurality of PLA continuous filaments onto a collection surface; andbonding the plurality of PLA continuous filaments to form the PLAspunbond nonwoven wherein the continuous filaments comprise ahydrophobic polymeric blend of the PLA and the at least one secondaryalkane sulfonate.
 19. The process of claim 17, wherein forming theplurality of PLA continuous filaments comprises forming bicomponentfibers having a side-by-side or sheath/core orientation.
 20. The processof claim 18, wherein the sheath comprises the blend of PLA and the atleast one secondary alkane sulfonate.
 21. The process of claim 18,wherein the at least one secondary alkane sulfonate has the followingstructure:

wherein n is a number between 7 and 16.